A transferred object rotating device includes a mounting plate having an opening corresponding to a shape of a transferred object and being capable of moving from a mounting position to a rotating position, a boost unit capable of moving up to pass through the opening of the mounting plate in the rotating position, and a rotation plate capable of rotating about a power transmission shaft. The mounting plate moves to the rotating position after the transferred object is mounted on the mounting plate to close the opening. The transferred object is lifted by upward movement of the boost unit. The transferred object rotates while being sandwiched between the boost unit and the rotation plate. The transferred object mounted on the mounting plate in the mounting position can be transferred to the rotating position by the mounting plate, and rotate in the rotating position.