The present invention provides a polymer compound which can constitute a photoresist composition which is capable of having an excellent resolution, forming a fine pattern with a good rectangularity, obtaining favorable resist characteristics even when acid strength of a acid generated from an acid generator is weak, and having favorable sensitivity; a photoresist composition including the polymer compound; and a resist pattern formation method using the photoresist composition. The photoresist composition and the resist pattern formation method use the polymer compound including an alkali soluble group (i), wherein the alkali soluble group (i) is at least one substituent group selected from an alcoholic hydroxyl group, a carboxyl group, or a phenolic hydroxyl group, and the substituent group is protected by an acid dissociable, dissolution inhibiting group (ii) represented by a general formula (1): —CH2—OCH2nR1   (1) (wherein R1 represents a cycloaliphatic group which contains no more than 20 carbon atoms and may contain an oxygen atom, a nitrogen atom, a sulfur atom, or a halogen atom, and n represents 0 or an integer of 1 to 5.).