Provided is an inhibitor for at least one kind of kinase selected from the group consisting of CDK7, CDK4, CDK6, PIM2, TSSK3, MST4, NEK6, MAP3K, MST3, DDR1, SPHK1, CaMK1, AurA, BRK, CaMK4, and PIM1, the inhibitor including as an active ingredient a compound represented by the following general formula (1) or a salt thereof: in the general formula (1), R1, R2, R3, R4, R5, and R6 are as described in Description.