A blow molding device comprising: a mold for blow molding; a blow nozzle to be inserted tightly into a mouth tube section of preform in a bottomed cylindrical shape, the preform being arranged to be inserted into the mold; a pressurized liquid feeding unit, the blow molding device being arranged to feed a pressurized liquid from the pressurized liquid feeding unit into the preform through the blow nozzle to form a container into an expanded shape along a cavity of the mold; and a valve mechanism (Vm), at a downstream end of a feed channel (Fs) for the liquid in the blow nozzle, configured to open the feed channel (Fs) in an opened state, wherein the pressurized liquid can be fed through the feed channel (Fs) into the preform, the blow molding device is characterized in that the valve mechanism is configured to close the feed channel (Fs) in a closed state, so that the liquid can circulate between the feed channel (Fs) and the pressurized liquid feeding unit in the closed state of the valve mechanism, and the blow molding device is further characterized in that it comprises a liquid circulating unit configured to adjust the liquid to a predetermined temperature and feed the liquid to the pressurized liquid feeding unit, wherein the feed channel (Fs) communicates in an openable and closable manner with the pressurized liquid feeding unit via an introductory passage provided in the blow nozzle at an upstream end of the feed channel (Fs) and communicates in an openable and closable manner with the liquid circulating unit via an exhaust passage provided at a downstream end at a position on an upstream side of the valve mechanism (Vm), and the liquid can circulate between the feed channel (Fs) and the pressurized liquid feeding unit via the liquid circulating unit. a mold for blow molding; a blow nozzle to be inserted tightly into a mouth tube section of preform in a bottomed cylindrical shape, the preform being arranged to be inserted into the mold; a pressurized liquid feeding unit, the blow molding device being arranged to feed a pressurized liquid from the pressurized liquid feeding unit into the preform through the blow nozzle to form a container into an expanded shape along a cavity of the mold; and a valve mechanism (Vm), at a downstream end of a feed channel (Fs) for the liquid in the blow nozzle, configured to open the feed channel (Fs) in an opened state, wherein the pressurized liquid can be fed through the feed channel (Fs) into the preform, the blow molding device is characterized in that the valve mechanism is configured to close the feed channel (Fs) in a closed state, so that the liquid can circulate between the feed channel (Fs) and the pressurized liquid feeding unit in the closed state of the valve mechanism, and the blow molding device is further characterized in that it comprises a liquid circulating unit configured to adjust the liquid to a predetermined temperature and feed the liquid to the pressurized liquid feeding unit, wherein the feed channel (Fs) communicates in an openable and closable manner with the pressurized liquid feeding unit via an introductory passage provided in the blow nozzle at an upstream end of the feed channel (Fs) and communicates in an openable and closable manner with the liquid circulating unit via an exhaust passage provided at a downstream end at a position on an upstream side of the valve mechanism (Vm), and the liquid can circulate between the feed channel (Fs) and the pressurized liquid feeding unit via the liquid circulating unit.