To provide a peroxycarboxylic acid ester photoinitiator, particularly a peroxycarboxylic acid ester photoinitiator derived from nitrogen contained aromatic heterocyclic carboxylic acid.

A peroxycarboxylic acid ester photoinitiator is expressed by the formula in which R1 is an alkyl group, and R2 is an aromatic heterocyclic ring containing a first sp2 orbit hybrid nitrogen atom and at least one kind of additional component selected from (i) an additional sp2 orbit hybrid nitrogen atom having trivalent bond formed of single bond and double bond so as to be conjugate to the first sp2 orbit hybrid nitrogen atom, (ii) an alkylperoxycarboxylic acid ester substituent, and (iii) an electron attractive substituent with Hammett's sigma value of 0.1 or more.