A polymerizable composition comprising: (A) a non-acrylic binder polymer having an ethylenically unsaturated bond on a side chain; (B) a neutrally charged compound capable of generating a radical under light or heat; and (C) a compound having an ethylenically unsaturated bond, and a polymerizable composition comprising: (A') a polyurethane resin having an ethylenically unsaturated bond on a side chain, which is a reaction product of an isocyanate compound and a diol compound including a diol compound represented by the formula (G) defiend herein; (B) a neutrally charged compound capable of generating a radical under light or heat; (C) a compound having an ethylenically unsaturated bond; (D') a 1,4-benzoquinone derivative; and (E') a dye having a maximum absorption wavelength in a region of from 350 to 450 nm.