Abstract: A magnetically driven, powerful rotary pump comprising at least one driven magnet secured to the rotary shaft of a pump and housed in a magnet case to separate the driven magnet in a liquid-type chamber from the pump chamber and at least two driving magnets secured to a drive shaft to be connected to a power source, with the at least one driven magnet being housed in the magnet case and being sandwiched in between the driving magnets. In one embodiment, the at least one driven magnet treated to be corrosion resistant and the magnet case is made of a corrosion resistant material or treated to be corrosion resistant, thereby rendering it unnecessary to form a liquid-tight seal between the pump chamber and the inside of the magnet case.