It is found that a nucleoside derivative represented by the following general formula (1) has an anti-viral activity and is less toxic to host cells. [in the formula, R1 represents a hydrogen or halogen atom, R2 represents a hydrogen or halogen atom, R3 represents a cyano group, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, a halogen atom, or an azido group, R4 represents an amino group, a hydrogen atom, a halogen atom, or a hydroxy group, R5 represents a nitrogen atom or a methine group, R6 represents a hydrogen atom or a hydroxy group, and R7 represents a hydrogen atom or a hydroxy group].