The prosecutors accuse Ronaldo of hiding the cash in offshore companies.
In a statement, they claim that Ronaldo knowingly used a "business structure" created in 2010 to hide income from image rights in Spain.
The accusations are based on a report from Spain's tax agency.
The 32-year-old follows in the footsteps of FC Barcelona forward and Argentina star Lionel Messi, who was found guilty of the same offence last year although the sums involved were smaller.
Ronaldo denies allegations
In December leaked documents suggested that Ronaldo had avoided tax on income allegedly held in offshore accounts.
He denied the allegations.
The Portugal star is back in the media spotlight because the Spanish prosecutor insists that he and his entourage "consciously" breached their tax obligations, which is why they are now in trouble with the law.
The issue of tax evasion has caused anger in a country only just emerging from a damaging economic crisis that has seen countless people lose their jobs and inequalities rise.
Ronaldo, the world's highest paid athlete according to Forbes magazine, earned 93 million dollars (82 million euros) from salary, bonuses and endorsements last year.