Liquid blow-molding method for delamination container

A liquid blow-molding method for molding a delamination container from a resin container material, the resin container material including an outer layer, an inner layer, and an ambient air introduction hole provided in the outer layer to communicate between the outer layer and the inner layer, and the delamination container including an outer layer body and an inner layer body laminated on an inner side of the outer layer body in a manner such that the inner layer body is separatable from the outer layer body, the liquid blow-molding method comprising:

• a container molding step of molding the resin container material into the delamination container by actuating a plunger pump in a positive direction and supplying a pressurized liquid into the resin container material;
• and
• an inner layer body separation step of separating the inner layer body from the outer layer body by actuating the plunger pump in a reverse direction and sucking the pressurized liquid, which has been filled in the delamination container, out of the delamination.