An acid generating agent represented by the following formula (1) or (2) is provided, which is included in chemically amplified resist compositions: wherein in the formula (1) and (2), X represents an unsubstituted or substituted alkyl group having 1 to 20 carbon atoms and selected from alkyl, haloalkyl and alkylsulfonyl, which may have at least one hydrogen atom substituted by an ether group, an ester group, a carbonyl group, an acetal group, a nitrile group, a cyano group, a hydroxyl group, a carboxyl group or an aldehyde group, or represents a perfluoroalkyl group having 1 to 4 carbon atoms; R6 represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a heteroatom selected from nitrogen, sulfur, fluorine and oxygen; m is an integer from 0 to 2; and A+ is an organic counterion.