GMB Scotland said the Queen was ahead of many employers when it came to rates for her lowest-paid workers.
It is calling on Prime Minister Tony Blair to follow her lead and introduce a minimum wage of £5 an hour.
The union will be making the demand during the Trades Union Congress in Blackpool this week.
The GMB highlighted a recent job advert which had been placed by the Royal Household.
It is seeking staff for the Palace of Holyroodhouse in Edinburgh, the Queen's official Scottish residence.
Pay rates for the jobs start at £5.15 an hour.
GMB Scotland regional secretary Robert Parker said: "The cleaners appear to be the lowest paid members of the Royal Household staff but they are receiving much more from Her Majesty than many Scottish employers are prepared to pay their Mrs Mops.
"Tony Blair's government should be taking a leaf out of the Queen's book too and making the minimum wage at least a fiver an hour."
The minimum wage currently stands at £4.10 an hour, but the government is planning to increase the rate by 10p an hour from 1 October.
The union said its Magic Fiver campaign had already persuaded the NHS and local authorities in Scotland to raise the wages of their lowest-paid workers to £5 an hour.
The Royal Household is seeking staff to work in the Palace's new art gallery and shop, which are due to open in November.
Other jobs advertised include wardens at £5.50 an hour, retail assistants at £5.50 an hour and a shop manager at £18,000 a year.