A blow molding process in which a gas is blown into a parison within a mold to inflate the parison, the parison makes intimate contact with a mold shaping portion to form a hollow molded product, and the gas within the hollow molded product is discharged for cooling, the blow molding process including setting an internal gas pressure of the hollow molded product to 5 to 8 kgf/cm2; and discharging a gas satisfying an expression, F≧10×W. while blowing, wherein F is a gas flow rate (N1/min) and W is a hollow molded product weight (g).