The invention provides a positive resist composition comprising, as base resins contained therein, (A) a polymer having a weight-average molecular weight of 1000 to 500000 and containing a repeating unit which contains a structure having a hydrogen atom of a carboxyl group thereof substituted with an acid-labile group having a cyclic structure and (B) a novolak resin of a substituted or an unsubstituted naphtholphthalein, and in addition, a photo acid generator. There can be provided a positive resist composition having an appropriate absorption to form a pattern on a highly reflective substrate, excellent characteristics in adhesion and implantation onto a non-planar substrate, a good pattern profile after light exposure, and an ion implantation resistance at the time of ion implantation; and a patterning process.