A blow molding mold unit comprising: a plurality of blow molds each including: a pair of split molds forming a plurality of cavities arranged in a row in a first direction, a plurality of bottom molds respectively corresponding to the cavities, and a bottom mold fixing plate to which the plurality of bottom molds are fixed, the plurality of blow molds being arranged in a second direction perpendicular to the first direction, first fixing members holding split molds that are arranged at both end positions in the second direction, the first fixing members being fixed to a mold clamping plate, second fixing members arranged between the first fixing members, and to which split molds other than the split molds fixed to the first fixing members are fixed, a push-up rod disposed below the bottom mold fixing plate, and a push-up member configured to be coupled to a lifting device and extending along the second direction below the second fixing members, the push-up member being configured to push up, via the push-up rod, the bottom mold fixing plate to lift the plurality of bottom molds arranged in the second direction.