A magnetic heating and cooling device is provided that comprises a heat exchanger that includes a magnetic body having a magnetocaloric effect; a magnetic field applying and removing unit that selectively applies to or removes from the magnetic body a magnetic field; and a liquid refrigerant moving unit that reciprocates a liquid refrigerant from one end to the other end, or from the other end to the one end, of the heat exchanger to exchange heat with the magnetic body inside the heat exchanger. The magnetic body is constituted by a plurality of flat magnetic members. At least one flat magnetic member has at least one slit that opens in the direction perpendicular to the movement direction of the liquid refrigerant, and the open end of each slit forms a corner to increase heat exchange efficiency.