According to one embodiment, an actinic-ray- or radiation-sensitive resin composition includes a resin (P) containing not only at least one repeating unit (A) that when exposed to actinic rays or radiation, is decomposed to thereby generate an acid and is expressed by any of general formulae (I) to (III) below but also a repeating unit (B) containing at least an aromatic ring group provided that the repeating unit (B) does not include any of those of general formulae (I) to (III). (The characters used in general formulae (I) to (III) have the meanings mentioned in the description.)