A magnetic pump having an internal magnet that is caused to rotate from outside its housing in order to cause rotation of the impeller. In a magnetic coupling structure in which an inner magnet disposed on an impeller is accommodated in a cylindrical accommodating portion of the housing, the outer circumferential surface of this accommodating portion is loosely inserted into the inner circumferential surface of a cylindrical outer magnet which is supported on its outer circumferential surface by a magnet cup body, and which rotates together with this magnet cup body, and the impeller rotates in accordance with the rotation of the outer magnet, and a cylindrical covering member which covers the inner circumferential surface of the abovementioned outer magnet is mounted on the outer magnet.