A positive resist composition comprising (A) a compound generating a specific sulfonimide compound by irradiation with an actinic ray or a radiation and (B) a resin having a group, which is decomposed by the action of an acid to increase the solubility of the composition in an alkali developer. The resist composition has an improved resolving power and an improved process allowance such as exposure margin and the depth of focus in a lithographic technique using a light source of short wavelengths capable of super fine working and a positive chemically amplified resist.