A compound obtained through Michael addition reaction of an α-aminoacetophenone skeleton-containing compound (I) represented by the following general formula (1) and a reactive compound (II) having a function as a Michael acceptor is used as a photopolymerization initiator. In the general formula (1), R1 represents an aliphatic group, R2 to R3 each independently represent an aliphatic group, etc., R4 to R7 each independently represent a hydrogen atom, X1 represents a single bond or a C1-6 alkylene group, X2 represents a carbonyl group, Y1 and Y2 represent a group represented by the following general formula (2). However, when Y1 and Y2 both have a structure represented by the general formula (2), X5 in at least one of them is —NH—. In the general formula (2), X3 and X4 each independently represent a linear or branched alkylene group having 2 to 6 carbon atoms, X5 represents a single bond, —O— or —NH—.