A blow molding apparatus for molding a bottomed cylindrical preform (PF), which is mounted in a blow molding mold (1), into a shape that conforms to the cavity (2) of the mold (1) by supplying a pressurized liquid (L) to the preform (PF) is provided with: a blow nozzle (13), which fits together with the cylindrical opening (PFb) of the preform (PF); a plunger pump (31) for supplying a pressurized liquid (L) to the preform (PF) through the blow nozzle (13); and a control unit (33) for keeping the peak pressure of the liquid (L) supplied into the preform (PF) between 3.5 MPa - 5.0 MPa during supply of the pressurized liquid (L) into the preform by changing the operating speed and operating force of the plunger pump (31).
