PURPOSE: To inexpensively produce a spherical molded product having a hollow part using an integral hollow injection molding method injecting a molten synthetic resin in a mold cavity and subsequently injecting gas to fill the mold cavity.

CONSTITUTION: A spherical molded product 2 having a hollow part 1 therein is integrally molded by a hollow injection molding method wherein a molten high impact polystyrene resin is injected in a mold cavity and gas is subsequently injected under pressure to fill the mold cavity. Therefore, the spherical molded product 2 can be inexpensively and easily produced.