A photoresist composition is disclosed containing an alkali-soluble resin and a photosensitive substance obtained by reaction of a polyhydroxy compound and (a) a 1,2-naphthoquinonediazido-5-(and/or -4-)sulfonyl chloride(s), said photosensitive substance being a mixture of photosensitive compounds (1) to (3):(1) a photosensitive compound having at least one hydroxyl group per molecule and having a number ratio of 1,2-naphthoquinonediazido-5-(and/or -4-)sulfonyl chloride sulfonate groups to hydroxyl groups within the range of from 3 to 20, contained in the photosensitive substance in an amount of 50 wt % or more;(2) a photosensitive compound where all the hydroxyl groups in the polyhydroxy compound have been 1,2-naphthoquinonediazidosulfonyl-esterified, contained in the photosensitive substance in an amount of 30 wt % to 0 wt %; and(3) a photosensitive compound having three or more hydroxyl groups which have not been 1,2-naphthoquinonediazidosulfonyl-esterified per molecule, contained in the photosensitive substance in an amount of 20 wt % to 0 wt %.The composition is suitable to exposure with g-ray, i-ray and excimer laser to provide a sharp resist image. The photoresist composition also has high sensitivity, high resolving power, precise reproducibility to provide resist images having good sectional shapes, broad development latitude, high heat resistance and good storage stability.