Provided is a blow molding device including a blow molding mold (1) to which a bottomed tubular preform (PF) is fitted, a blow nozzle (13) that is fitted to a mouth tubular portion (PFb) of the preform (PF) fitted to the mold (1), and a pressurized liquid supply unit (22) configured to supply a pressurized liquid (L) to the blow nozzle (13). The preform (PF) is to be molded into a shape conforming to a cavity (2) of the mold (1) by filling the liquid (L) into the preform (PF) through the blow nozzle (13). The blow molding device further includes: a deaeration mechanism (30) that is connected to the blow nozzle (13). The liquid (L) is filled into the preform (PF) through the blow nozzle (13) after air that is present within the preform (PF) fitted to the mold (1) is sucked out by the deaeration mechanism (30).
