To provide a positive resist composition having a wide exposure latitude, from which a good profile can be formed not only by normal exposure but by immersion exposure, and to provide a pattern forming method using the composition.

The positive resist composition contains: (A) a resin having a specified repeating unit having a cycloalkyl group in a side chain, the solubility of the resin with an alkali developing solution increased by an action of an acid, by 50 to 99.7 mass% with respect to the whole solid content of the positive resist composition; (B) a compound generating an acid by irradiation with active rays or radiation; (C) a resin having at least one of a fluorine atom and a silicon atom; and (D) a solvent. The resin (C) is at least one of: a resin containing at least one of a fluorine atom and a silicon atom and having an alicyclic structure; and a resin that contains a repeating unit having at least one of a fluorine atom and a silicon atom in a side chain and contains a repeating unit having an unsubstituted alkyl group in a side chain. The pattern forming method is carried out by using the composition.