An in-die cover forming method for integrally forming a cover member with a surface of a base member in a die is provided. The die including an upper die half and a lower die half. The upper die halves are movable relative to each other. The base member is set on the lower die half such that its back is opposed to the lower die half. Using position determining mechanisms located between the lowerdie half and the back of the base member, the position of the surface of the base member in relation to the lower die half in the die moving direction is determined. The cover member is placed betweenthe base member and the upper die half. The cover member is integrated with the surface of the base member by closing the upper die half with respect to the lower die half while pressing the cover member against the base member through vacuuming.