Disclosed is a positive photoresist composition comprising an alkali-soluble resin and 1,2-naphthoquinonediazide-5-(and/or -4-)sulfonic esters of a polyhydroxy compound having a particular structure consisting of 5 aromatic rings linked linearly, in which each of the aromatic rings contains a hydroxyl group and the respective aromatic rings next to both the terminal rings contains a substituent group at the 5-position to the hydroxyl group thereof. The positive photoresist composition which has high resolution, low dependence of the resolution on film thickness, and broad latitude of development, leaves little development residue, and has very excellent storage stability without separation of photosensitive materials and generation of microgel (no increase in particle) with a lapse of time.