The invention discloses a microwave oven drainage device and a microwave oven comprising the drainage device. The drainage device includes a first drainage part and a water receiving box, the first drainage part is provided with a first groove, one or a plurality of first fastening piece hole and at least one first drain port; and the water receiving box is connected with one end, which is provided with at least one first drain port, of the first drainage part, wherein the at least one first drain port is in fluid connection with the water receiving box. The drainage device can effectively discharge water vapor formed in the microwave oven (especially a steam microwave oven) during the cooking process to avoid short circuit of electric components, ensure the normal operation of the microwave oven, and keep the microwave oven clean.