Method and apparatus for producing resin container

A method of producing a resin container, the method comprising:

• injection-molding a resin intermediate molded body of bottomed cylindrical shape as a first injection-molding;
• injection-molding a resin material on an outer side of the intermediate molded body as a second injection molding, to produce a multilayer preform in which a resin layer is layered on an outer peripheral side of the intermediate molded body;
• blow-molding the preform in a state of containing residual heat from injection-molding to produce a resin container having a bottom portion thicker in wall thickness than a body portion, wherein
• a portion of an inner peripheral side of the intermediate molded body, the portion reaching a bottom portion of the intermediate molded body, has a tapered region in which a wall thickness increases toward the bottom portion;
• and
• the wall thickness of the bottom portion of an outer layer in the multilayer preform is set to be thicker than the wall thickness of the bottom portion of an inner layer excluding the tapered region.