Abstract: Provided is an actinic ray-sensitive or radiation-sensitive resin composition that can provide a pattern having good cross-sectional rectangularity. The actinic ray-sensitive or radiation-sensitive resin composition includes: a resin having a group that is decomposed by the action of an acid to generate a polar group; an onium salt (I) that generates an acid represented by formula (1) upon irradiation with actinic rays or radiation; and an onium salt (II) having at least one structural moiety W that includes an anionic moiety A and a cationic moiety M and forms an acidic moiety represented by HA upon irradiation with the actinic rays or radiation. The acid dissociation constant derived from the acidic moiety represented by HA and formed by replacing the cationic moiety in the structural moiety W with H+ is larger than the acid dissociation constant of the acid represented by formula (1).