An actinic ray-sensitive or radiation-sensitive resin composition and a pattern forming method using the composition are provided, the composition including (A) a resin containing a repeating unit having a group represented by formula (1) as defined in the specification, the resin being capable of increasing a solubility of the resin in an alkali developer by an action of an acid, and (B) a compound capable of generating an acid upon irradiation with an actinic ray or radiation; and a polymerizable compound represented by formula (M-1) as defined in the specification and a polymer compound obtained by polymerizing the polymerizable compound are provided.