A positive resist composition comprising 1,2-quinonediazide compound and, as an alkali-soluble resin, an alkali-soluble resin (A) which comprises a resin (I) obtainable through a condensation reaction of a mixture of m-cresol, 2,3,5-trimethylphenol and optionally p-cresol with an aldehyde and a low molecular weight novolak (II) having a weight average molecular weight of 200 to 2000 as converted to polystyrene, an alkali-soluble resin (B) which comprises a resin (I) and a compound of the general formula (III): ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 are respectively a C.sub.1 -C.sub.5 alkyl group or a C.sub.1 -C.sub.5 alkoxy group, 1, m and n are respectively a number of 0 to 3, R' is a hydrogen atom or a C.sub.1 -C.sub.3 alkyl group, or an alkali-soluble resin (C) which comprises a resin (IV) obtainable through a condensation reaction of a mixture of m-methoxyphenol and 2,3,5-trimethylphenol in a molar ratio of 80:20 to 30:70 with an aldehyde, which has good sensitivity, improved resolution and heat resistance.