PURPOSE: To reduce the production cost of a composite container consisting of cardboard and plastic by erecting at least two sections of an outside portion comprising cardboard and bending them to form a jacket including the cardboard and performing the blow molding of a polymer inside the jacket.

CONSTITUTION: At least two sections of an outside portion comprising cardboard are erected to be bent to form a jacket including cardboard blanks 11 and comprising at least two sections. A pair of the blanks arranged in opposed relationship are inserted in the separated and opened paired members 31, 32 of a mold. When the wheel of the mold is positionally aligned with a parison, the paired members 31, 32 of the mold are closed and the parison 40 is expanded and, after a proper cooling period, the mold is opened in a rotary release station. The integrated unit of the parison and the blanks is received in a separate transport mechanism.