A novel compound is a highly-sensitive photopolymerization initiator with excellent stability, low sublimability, excellent developability, and high transmittance in the visible region. It efficiently absorbs, and is activated by, near-ultraviolet rays such as at 365 nm. Also provided are a photopolymerization initiator and a photosensitive composition using such compound. An oxime ester compound is represented by the following general formula (I), a photopolymerization initiator containing the same, and a photosensitive composition containing the photopolymerization initiator and a polymerizable compound having an ethylenically unsaturated bond: R1 and R2 each represent R11, COR11, CONR12R13, CN, etc.; R11, R12, and R13 each represent a C1-20 alkyl group, etc.; R3 and R4 each represent R11, OR11, COR11, CONR12R13, OCOR11, CN, a halogen atom, etc.; a and b each represent an integer 0-4; X represents an oxygen atom, a sulfur atom, etc.; and R5 represents OH, COOH, or a group represented by general formula (II).