The invention provides a novel compound useful as a highly-sensitive photopolymerization initiator that has excellent stability, low sublimability, excellent developability, and high transmittance in the visible region and that 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 the above-described compound. Specifically, the invention provides an oxime ester compound 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:

wherein, R 1 and R 2 each represent R 11 , COR 11 , CONR 12 R 13 , CN, etc.; R 11 , R 12 , and R 13 each represent a C 1-20 alkyl group, etc.; R 3 and R 4 each represent R 11 , OR 11 , COR 11 , CONR 12 R 13 , OCOR 11 , CN, a halogen atom, etc.; a and b each represent an integer of 0 to 4; X represents an oxygen atom, a sulfur atom, etc.; and R 5 represents OH, COOH, or a group represented by general formula (II).