To regularly and efficiently perform production when a hollow molded product is to be molded while inserting a part in a die slide injection process to enhance the yield of a product.

The manufacturing apparatus 7 for the hollow molded product is equipped with an injection molding means 8 equipped with a fixed mold 13 and a movable mold 14, a part stocking part 10 for stocking the valve 4 and the terminal 5 to be inserted in a side winker 1 molded by the injection molding means 8, a robot 9 operated in order to insert the part taken out of the part stocking part 10 into a housing 3 and a part checking part 15 for confirming whether the robot 9 takes out the part from the part stocking part 10 in a predetermined posture.