To provide a mechanical stopper device having high maintainability in which an oscillating body 4 and buffer materials 5, 6, which receive impact force caused by the operation as the mechanical stopper device, can be easily replaced in a short period of time.

The mechanical stopper device is composed so as to set mechanical rotation limits of relative rotation members 1, 2 by providing a rotating shaft part such that the relative rotation is executed between the two relative rotation members 1, 2 around the rotation axial center 10. The mechanical stopper device has the following characteristics. An arcuate groove 11, which has the end parts 12, 13 around the rotation axial center 10, is provided to the first relative rotation member 1 of the relative rotation members 1, 2. The two buffer materials 5, 6, which are slidable on the groove 11 between the end parts 12, 13, are provided to the groove 11. The oscillating body 4, which is slidable on the groove 11 between the end parts 12, 13 of the groove 11, is provided between the two buffer materials 5, 6. A stopper 3, which is brought into contact with the oscillating body 4 depending on the rotational position of the second relative rotation member 2, is provided to the second relative rotation member 2 of the relative rotation members 1, 2. A window 16, to which the oscillating body 4 and the two buffer materials 5, 6 can be inserted, is provided to the first relative rotation member 1.