Provided is a new compound with excellent MMP inhibitory effect and reduced side-effects. The compound is a matrix metalloproteinase inhibitor with, as an active ingredient, the hydroxamic acid derivative represented by general formula (1), or a salt thereof. (1) (In the formula, R1 represents an (E)-3-phenylallyl group or a 3-phenylpropyl group； R2 represents a hydrogen atom, an isobutyl group, a 2-(4-methoxyphenyl) ethyl group, or the like； R3 represents a 1H-indole-3-yl group, a 1-napthyl group, or the like； and R4 represents a methyl group, a benzyloxy group, a hydroxy group, a phenethyl group, or the like.)
