Disclosed are a highly sensitive photopolymerization initiator composition having excellent storage stability, a photosensitive composition containing the photopolymerization initiator composition, and a thiourethane compound suitable for the photopolymerization initiator composition. Specifically disclosed is a thiourethane compound having 2-6 units each containing a moiety represented by the formula (i) below and a moiety represented by the formula (ii) below. (i) (ii) (In the formulae, R1 represents a hydrogen atom or a methyl group; and R2 represents -CO-, -COO- or -COOR3- (wherein R3 represents an alkylene group having 2-6 carbon atoms).