There is provided a compound represented by a general formula (B1-1) shown below, an acid generator composed of the above compound, a resist composition containing an acid generator composed of the above compound, and a method of forming a resist pattern: (wherein RX represents a hydrocarbon group which may contain a substituent group; Q1 represents an alkylene group of 1 to 12 carbon atoms which may contain a substituent group, or a single bond; n represents an integer of 0 or 1; Y1 represents an alkylene group of 1 to 4 carbon atoms, or a fluorinated alkylene group of 1 to 4 carbon atoms; and A+ represents an organic cation which contains a nitrogen atom).