A blow mold includes: a pair of movable molds for forming engagement grooves of a container body; and advancing/retreating mechanism units for advancing and retreating the movable molds between a standby position and a molding position. The advancing/retreating mechanism units are equipped with drive shafts to which the movable molds are fixed and which are rotatably supported with respect to a cavity mold; actuator devices which each have a linear-motion shaft capable of advancing and retreating in a direction orthogonal to the drive shaft and which are each swingably provided with respect to the cavity mold; and link members each having an end side fixed to the drive shaft outside the cavity mold and an opposite end side coupled to the linear-motion shaft.