Resist composition and method of forming resist pattern

A resist composition comprising a base component (A) which exhibits changed solubility in a developing solution under the action of acid and an acid-generator component (B) which generates acid upon exposure,

• the base component (A) comprising a polymeric compound (A1) comprising a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a1) containing an acid decomposable group which exhibits increased polarity by the action of acid:
• wherein R1 represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;
• W represents —COO—, a —CONH— group or a divalent aromatic hydrocarbon group;
• Y1 and Y2 each independently represents a divalent linking group or a single bond;
• R′1 represents a hydrogen atom;
• R′2 represents a methyl group;
• and R2 is a group represented by general formula (3-1) shown below:
• wherein A′ represents an oxygen atom;
• a represents an integer of 0 to 2;
• and R8 represents an alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkl group or a cyano group, wherein R″ represents a hydrogen atom or an alkyl group.