The purpose of the present invention is to provide a triazine derivative represented by formula (I) or a pharmaceutically acceptable salt thereof. (In the formula, R1 represents a lower alkyl group which may have a substituent； R2 represents a hydrogen atom or a lower alkyl group which may have a substituent； A represents a nitrogen atom or C-R3； R3 represents a hydrogen atom, a cyano group, an acyl group which may have a substituent, a sulfonyl group which may have a substituent or a carbamoyl group which may have a substituent； and R4 represents a lower alkyl group which may have a substituent or a cycloalkyl group which may have a substituent.)
