An object of the present invention is to provide a sulfonium salt that has sufficient photosensitivity by active energy rays, such as visible light, ultraviolet rays, electron beams, and X-rays. The present invention is a sulfonium salt represented by formula (1). It is noted that R1 is a group represented by formula (2); R2 and R3 each represent an aryl group having 6 to 30 carbon atoms, a heterocyclic hydrocarbon group having 4 to 30 carbon atoms, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms; X− represents a monovalent polyatomic anion; R4 to R6 each represent an alkyl group, or the like; k represents an integer of 0 to 4; m represents an integer of 0 to 3; n represents an integer of 0 to 4; and A represents a group represented by —S—, —O—, —SO—, —SO2—, or —CO—.