The invention provides a high-resolution resist material comprising an acid generator that has high sensitivity and high resolution with respect to high-energy rays of 300 nm or less, has small line-edge roughness, and is superior in heat stability and in shelf stability, and provides a pattern forming method that uses this resist material. The invention further provides a chemically amplified positive resist material comprising a base resin, an acid generator and a solvent in which the acid generator generates an alkylimidic acid containing a fluorine group, and provides a pattern forming method comprising a step of applying the resist material to the substrate, a step of performing exposure to a high-energy ray of a wavelength of 300 nm or less through a photomask following heat treatment, and a step of performing development by a developing solution following heat treatment.