Spain strolled their way to three wins from three and top spot in Group H as their second string beat a poor Saudi Arabia outfit in Kaiserslauten.
Having enjoyed a wealth of possession, the only surprise was that Juanito's header was the only goal at half-time.
Mabrouk Zaid produced a string of saves in the Saudi goal, with Joaquin, Jose Antonio Reyes and David Albelda denied.
However, a late Saudi surge did cause Spain some discomfort, with Saad Al Harthi firing a fine chance over.
The result means Spain will face France, who finished runners up in Group G behind Switzerland, in the second round on 27 June in Hanover (2000 BST).
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Saudi Arabia knew before kick off they had to score at least four goals to stand a chance of qualifying, but survival was clearly priority number one as they allowed Spain, who had changed their entire first XI, to feel their way into the match.
With Cesc Fabregas pulling the strings in midfield and Joaquin particularly dangerous on the right flank, Luis Aragones' side created a host of chances in the first half.
Joaquin (twice), Reyes and Albelda all forced Zaid into full-length saves from range, while Raul was a constant nuisance with his movement and touch on his first start in these finals.
With the Saudis clearly reluctant to commit players forward, it was only a matter of time before Spain took the lead and so it was when defender Juanito rose unmarked to power home the opener with his head.
Even that failed to ignite Saudi Arabia's forward play, though Sami Al Jaber did enjoy a rare foray forward on 40 minutes that ended with a tame shot.
With Fabregas and Reyes also stinging Zaid's palms before half-time, the only surprise was that Marcos Paqueta's outfit conceded just one goal in the first 45.
In truth, Saudi Arabia started in better form in the second, with Spain having to defend their lines on more than one occasion.
Hussein Sulimani twice brought decent saves from Santiago Canizares from range, while Nawaf Al Temyat thought he had earned the Saudis a penalty - until he was shown a yellow card for diving over Carlos Marchena's tackle.
With Spain showing a tendency to over-complicate their forward play, they were unable to enjoy a more comfortable end to the game.
And after Fernando Torres, David Villa and Antonio Lopez had wasted decent chances, Al Harthi could have snatched the most unlikely of draws at the death when he collected Mohamed Noor's pull-back.
However, he spooned harmlessly over from six yards to make it 10 matches without a win in World Cup finals for Saudi Arabia.
Saudi Arabia: Zaid, Dokhi, Tukar, Al Montashari, Khathran, Sulimani (Massad 81), Noor, Khariri, Aziz (Al Temyat 13), Al Jaber (Mouath 68), Al Harthi.
Subs Not Used: Al Anbar, Al Bahri, Al Daeyea, Al Qadi, Ameen, Khojah.
Booked: Al Jaber, Al Temyat.
Spain: Canizares, Salgado, Marchena, Antonio Lopez, Juanito, Albelda, Reyes (Torres 69), Iniesta, Joaquin, Fabregas (Xavi 66), Raul (Villa 45).
Subs Not Used: Casillas, Pernia, Puyol, Luis Garcia, Alonso, Sergio Ramos, Senna, Pablo, Reina.
Booked: Albelda, Reyes, Marchena.
Goals: Juanito 36.
Att: 46,000
Ref: Coffi Codjia (Benin).
Fifa man of the match: Juanito
TRIVIA
Spain have now won seven consecutive group matches at the World Cup. This is the third time they have started the finals with three straight victories, following 1950 and 2002. Spain are now unbeaten in 25 matches, and have not lost since 22 June 2004, when Portugal beat them 1-0 at Euro 2004.
Spain's longest unbeaten streak is 31 between September 1994 and January 1998 under coach Javier Clemente. They're unbeaten in 10 World Cup matches, winning seven and drawing three. Together with Brazil, who have won 10 straight, they hold the longest running unbeaten sequence. The all-time record is 13 unbeaten matches by Brazil (1958-1966).
Saudi Arabia's winless streak at the World Cup was extended to 10 matches. The last time they won a match at the World Cup was on 29 June 1994 when they defeated Belgium 1-0.
Trivia stats source: Infostrada Sports