PURPOSE: To obtain a new ascorbic acid derivative excellent in solubility to water, etc., and useful as an ingredient of cosmetics capable of preventing e.g. dermal wrinkles due to aging by light.

CONSTITUTION: This new ascorbic acid derivative is a compound of formula I (R1 and R2 are each H, an alkyl, etc.; X is H, Na, K, Ca, etc.; Y is H, Na, K, Ca, etc.) (e.g. potassium 5,6-O-benzylidene ascorbate phosphate) and is obtained by reaction of the hydroxyl groups on the 5 and 6 sites of ascorbic acid with a methylidene derivative (e.g. benzylidene dimethylacetal) followed by reaction with phosphorus oxychloride.