Even when the filling speed increases, the surface temperature of a molded bottle falls within a constant range, and a sterilizer adequately sterilizes the bottle. A preform is heated, the heated preform is sealed in a mold, the preform sealed in the mold is blow-molded into a bottle, the surface temperatures of a neck portion, a body portion, and a bottom portion of the molded bottle are measured, and the mold temperatures of a neck portion, a body portion, and a bottom portion of the mold is so adjusted that the measured surface temperature of the bottle falls within a specified temperature range.