PURPOSE: To mold a hollow article such as a bottle made of beautiful polypropylene which is transparent, glossy and even in thickness through biaxial orientation blowing method, by eliminating completely molten crystalline substance contained in molten polypropylene in an injection cylinder by kneading the molten polypropylene prior to pouring of the same into a metal die.

CONSTITUTION: Simultaneously with elimination of crystalline substance by mixing amorphous substance and crystalline substance of polypropylene in a molten state with a rotation of an injection screw uniformity of a temperature is contrived and nonuniformity of an inner temperature in a parison is eliminated. At the time of molding of the parison, a thin coating is made to form on the inner and outer surfaces of the parison by making injecting and cooling time as short as possible, and cooling is left within a limit through which the parison is capable of releasing from a metal die. The hot parison released from the metal die is adjusted immediately to a molding temperature by a heat exchanger type temperature adjusting device. A biaxial orientating hollow article, which is superior in transparency, is molded by orientation blow molding, by a method wherein an orientation blow of the article is made rapidly and let the article cool quickly.