To provide a sewage treatment apparatus capable of simply and certainly replacing an electrode in a short time.

A sewage treatment apparatus D1 is equipped with a sewage housing tank 1, an electrode cartridge 2 and a DC power supply (not shown in a drawing). The cartridge 2 has two sets of electrode main bodies 3, 4, a holder 12 for holding electrode main bodies and the handle 13 for possessing the holder 12. A pair of engaging parts 16 are arranged in the outer surfaces of the opposed side parts of the holder 12. One-action operation type fixing metal fittings 17 are arranged in the outer surfaces of the upper parts of one set of the opposed side walls 6, 7 of the sewage housing tank 1 and engaged with the engaging parts 16 of the cartridge 2 arranged so as to be partially housed in the sewage housing tank 1 in a detachable manner. The cartridge 2 is fixed to the sewage housing tank 1.