A positive photoresist composition which comprises (A) a resin having a group which decomposes by the action of an acid to increase solubility in an alkaline developing solution, and (B) a compound which generates an aliphatic or aromatic carboxylic acid substituted with at least one fluorine atom upon irradiation with an actinic ray or radiation. The positive photoresist composition of the present invention is improved in resolution and process allowance such as exposure margin and depth of focus in a lithographic technology using a light source having a short wavelength capable of conducting the ultra fine fabrication and a chemical amplification-type positive photoresist. Further, it exhibits the excellent performance when an electron beam is used as a light source for exposure.