A Photoresist composition comprising a polymer comprising a structural unit derived from a compound represented by the formula (I): wherein R1 represents a hydrogen atom or a methyl group, R2 represents a C6-C12 aromatic hydrocarbon group which can have one or more substituents, R3 represents a cyano group or a C1-C12 hydrocarbon group which can have one or more substituents and which can contain one or more heteroatoms, A1 represents a single bond, —(CH2)g—CO—O—* or —(CH2)h—O—CO—(CH2)i—CO—O—* wherein g, h and i each independently represent an integer of −1 to 6 and * represents a binding position to the nitrogen atom, a resin having an acid-labile group and being insoluble or poorly soluble in an aqueous alkali solution but becoming soluble in an aqueous alkali solution by the action of an acid, and an acid generator.