The blow molded preform of a laminated wall structure comprises a bulging shoulder portion which has a diameter that widens slightly in the downward direction; a bottom shell portion for molding a bottom, which has been blow molded from a corresponding portion of a parison so as to have a widened and deformed shape; an inner overhang wall portion in any position starting from the opposite side of a neck ring and ending at the upper portion of a bulging shoulder portion, with an inner wall portion having a diameter that widens in the downward direction; and/or a radially widened connecting portion of an arced shape, which has a larger diameter than a barrel portion so that the entire bottom including a bottom shell portion takes a bulging spherical shape.