The present invention provides a novel antimetabolic anticancer agent that has an excellent balance between antitumor effect and toxicity. Specifically, the present invention provides a medicament containing, as an active ingredient, a 5-fluorouracil derivative represented by Formula (I) or a salt thereof:wherein R1 represents a hydrogen atom or a protecting group of a hydroxy group, R2 represents a lower alkoxy-lower alkyl group or a tetrahydrofuranyl group, X represents a carbon atom or a nitrogen atom, and Y represents a halogen atom or a cyano group.
