To provide a polymerizable composition suitable for a lithographic printing plate precursor which can satisfy the requirements of high sensitivity, excellent storage stability and long press life and enables direct plate making from digital data from computer, etc. when recording is conducted a solid laser or semiconductor laser emitting ultraviolet ray, visible light or infrared ray and a compound therefore, the present invention relates to a photoradical polymerizable composition comprising a polyfunctional crosslinking agent having a specific structure represented by formula (I) or (II) defined in the specification.