PURPOSE: To obtain a hollow container having improved dimensional stability and little shrinkage with time efficiently, by utilizing the instantareous temperature rise due to the adiabatic compression of air in molding the container from a thermoplastic resin according to the orientation blowing.

CONSTITUTION: The preform 1 adjusted to the softening temperature is charged into the split molds 2 and 2 with the opening held, and air is blown into the preform 1 by advancing the piston 12 of the air cylinder 11 in the direction of arrow. When the piston 12 advances from the position A to the position B, the preform 1 is brought into contact with the cool surfaces 3 of the molds 2 and 2, molded into the form of the desired container, cooled, and solidified. When the piston 12 is advanced to the position C, the air in the container is pressurized, and the temperature rises rapidly, to heat the container to a temperature above the glass transition point, and the internal stress produced in the blow molding is removed. The release valve 6 is when opened to reduce the pressure, and the mold is opened to take out the container.