The invention relates to a sewage treatment device and a sewage treatment method. The device comprises a housing, aerators arranged at the bottom of the housing, first deflectors, sludge hoppers, a water distribution channel, second deflectors, precipitate inclined plates, overflow tanks and clear water tanks. The two first deflectors perpendicular to the bottom of the housing sequentially divide the inner cavity of the housing into a first aerobic reaction zone, an anoxic reaction zone and a second aerobic reaction zone. When the device is working, sewage flows from a water outlet from the wall surface of the water distribution channel to the anoxic reaction zone, and then flows to the first and second aerobic reaction zones through the gaps between the first deflectors and the bottom of the housing; the sewage is aerated by the aerators; one part of the sewage is refluxed to the anoxic reaction zone from the upper parts of the first deflectors, and the other part flows into the sludge hoppers through deflector holes; after reaction precipitation, sewage is discharged from through holes at the tips of the sludge hoppers, and is circulated again; clear water flows through the precipitate inclined plates and is gradually overflown; the clear water is discharged to the clear water tanks through the overflow tanks, and is discharged to the outside. The device provided by the invention has the advantages of simple structure, convenient operation, regular flow pattern, high sludge concentration, high oxygen dissolution efficiency, low energy consumption, low construction cost, and low operation cost.