To solve a problem associated with formation of a transparent window portion in a biaxially stretch blow molded container by a nozzle structure of an injection molding apparatus, provided is a biaxially stretch blow molded container that is formed with a clearly transparent window portion in a longitudinal strip shape by effectively preventing mixture and cut-in of a colored resin to the window portion. In a predetermined range extending from an upstream end to a predetermined downstream position of a flow path including a cylindrical flow path and a reduced-diameter flow path formed in a nozzle portion, a pair of guiding ribs in the form of longitudinal ridges is arranged in line to partition the flow path in a circumferential direction, and a longitudinal groove flow path is formed between the pair of guiding ribs. A molten B resin is supplied to the longitudinal groove flow path, and a molten A resin is supplied to the cylindrical flow path excluding the longitudinal groove flow path. Thus, the longitudinal strip-shaped flow path of the B resin interrupts the cylindrical flow path of the A resin in the circumferential direction.