Photoresist composition, a resist pattern forming method, the polymer and compound

The present invention is a photoresist composition containing a polymer, and [B] acid generator having a structural unit represented by [A] below equation (1). In the following formula (1), R R R [A] The polymer, lactone structure, further having a structural unit comprising at least one structure selected from the group consisting of cyclic carbonate structure and sultone structure preferred. [A] The polymer preferably further has a structural unit represented by the following formula (2).