A blow mold method for a double-walled container, including: blowing in which an intermediate molded article is molded by stretch blowing a preform housed in a die; and pressing in which the intermediate molded article is pressed inside the die and a double-walled container is molded. During the pressing, an internal floor-corresponding section is pressed such that internal wall-corresponding section is inverted as far as the inside of an outer wall-corresponding section, in a state in which heat retention is maintained such that the internal wall-corresponding section can be inverted as far as the inside of the outer wall-corresponding section.