PURPOSE: To obtain the negative type photoresist composition high in sensitivity and resolution and small in fluctuation of performance due to processing conditions after exposure by incorporating a specified resin and a specified compound, etc.

CONSTITUTION: This photoresist composition comprises the water-insoluble and alkali-soluble resin A, preferably, such as novolak phenol resins, the compound B to be allowed to produce an acid by irradiation of active rays or radiation, such as known compounds and mixtures of them, the compound C having at least one group capable of cross-linking by action of an acid, and the compound D producing a base at a heating temperature of ≥50°C, preferably, ≥70°C. The compound to be selected as the compound C includes the compound reducing solubility of the novolak resin in alkali by the cross-linking reaction or polymerization reaction, such as a compound having a methylol group as a formaldehyde precursor.