A positive resist composition sensitive to radiations such as ultraviolet rays, far ultraviolet rays, which comprises; an o-quinonediazide compound; and a novolac resin(1) obtained by allowing an aromatic aldehyde of the formula(I) ##STR1## wherein R.sub.4 to R.sub.6 represents hydrogen, alkyl, cycloalkyl, alkoxy, alkenyl or aryl, k'0 represents an integer not smaller than 0 and p represents 1, 2 or 3, to react with a phenol compound of the formula (II) ##STR2## wherein R.sub.7 to R.sub.9 represents hydrogen, hydroxy, alkyl, cycloalkyl, alkoxy, alkenyl or aryl, provided that at least one of R.sub.7 to R.sub.9 is cycloalkyl having 6 or less carbon atoms, in the presence of an acid catalyst to obtain a reaction product(1) containing low molecular weight ingredients; and, then, allowing the reaction product(1) to further react with a phenol compound(1) and formaldehyde.