A polymer comprising recurring units of butyrolactone (meth)acrylate, recurring units having a carboxyl or phenolic group which is substituted with an acid labile group, and recurring units having a phenol group or an adhesive group in the form of 2,2,2-trifluoro-1-hydroxyethyl is quite effective as a base resin for resist. A positive resist composition comprising the polymer is improved in such properties as a contrast of alkali dissolution rate before and after exposure, acid diffusion suppressing effect, resolution, and profile and edge roughness of a pattern after exposure.