A pentafluorobutane composition includes, with respect to 100 parts by weight of 1,1,1,3,3-pentafluorobutane: 0.1 to 5.0 parts by weight of at least one of nitromethane and nitroethane; and 0.1 to 5.0 parts by weight of at least one of 1,3-dioxolane, trimethoxymethane, trimethoxyethane, and 1,2-butylene oxide.