A magnetic clamping device is provided with a magnetic force generating mechanism at which a housing cover body comprising soft magnetic material is arranged centrally at a hollow housing portion, a nonmagnetic metal frame body comprising a nonmagnetic body is made to engage with the outside circumference thereof, a plurality of arcuate nonreversible permanent magnets are arranged in annular fashion within an annular magnet housing space at the back of this nonmagnetic metal frame body, a reversible permanent magnet and a magnetic polarity switching coil disposed peripherally with respect thereto are provided at the back of the housing cover body, and a base cover body that blocks a back opening of the hollow housing portion is provided, the magnetic clamping device being characterized in that the metal frame body is joined in integral fashion to the housing cover body and the baseplate.