Abstract: A photosensitive resin composition which comprises (1) an ethylenically unsaturated compound which can be addition polymerized to form a high molecular compound, said addition polymerizaton being initiated by a free radical and of chain-propagation, (2) a 2-polycyclic aryl-4,5-diphenylimidazolyl dimer wherein the polycyclic aryl group comprises at least two benzene rings condensed each other and (3) at least one compound selected from the group consisting of dimedone, indolacetic acid, N-naphthylglycine, S-lower alkylthioglycollic acid, 4,4'-bis[di(lower)alkylamino]benzyl, p-di(lower)alkylaminobenzoic ester, leucocrystalviolet, indoxylic acid, rhodanine, 7-di(lower)alkylaminocumarine and diarylthiourea and their derivatives, the molar ratio of the component (2) and the component (3) being from 2:1 to 1:5.