In addition to comprising a cavity surface (2), this blow molding mold (1) is configured so that a preform (4) can be installed and is configured so as to be mountable on a blow molding device (10) having: a pressurized liquid supply function for molding a container (3) by supplying a pressurized liquid (L) and extending the preform (4) towards the cavity surface (2); and a head space-forming function for forming a head space (Hs) in the container (3) by drawing back some of the liquid (L) filled inside the container (3) from the blow nozzle (12) or withdrawing an extending rod (14) from the container (3) that is filled with the liquid (L). The blow molding mold is characterized in that: the cavity surface (2) is provided with a bottom-forming surface (2a), a body-forming surface (2b), a shoulder-forming surface (2c), and a mouth-forming surface (2d); and the body-forming surface (2b) is provided with flat sections (2b5) that have a flat cross-sectional shape.
