To provide a positive photoresist composition having high resolving power in the production of a semiconductor device, having evaluation with the same light exposure near the margin of resolution by which the size in which a nondense pattern vanishes and the marginal resolution size of a dense pattern show approximate values closer to each other and ensuring low surface roughness of a line pattern.

The positive photoresist composition contains a resin containing repeating units with a specified structure and having solubility to an alkali developing solution increased by the action of an acid, a compound which generates the acid when irradiated with active light or radiation and an organic solvent which dissolves the above components.