Philip, who famously writes his books in a shed at the bottom of his garden, was up against lots of top adult authors, but the judges said he was the "overwhelming" winner.
The Amber Spyglass is the third part of Philip Pullman's His Dark Materials trilogy. They tell the story of plucky heroine Lyra, her daemon Pantalaimon and her best friend, Will.
Children's book of the year
Together the three pals take on dark forces to save the world from destruction, and The Amber Spyglass sees them involved in the ultimate good vs evil battle.
Philip Pullman also won the Whitbread Children's Book of the Year. But then all the winners of the different categories were put together for the overall Whitbread Book of the Year prize - and he won that too.