The invention discloses a sewage treatment device, which comprises a machine body, a liquid chlorine box and a chlorine adding device, wherein the liquid chlorine box is arranged at the top of the left side of the machine body; the chlorine adding device is arranged at the top of the right side of the machine body; a liquid chlorine cavity in downwards extending arrangement is arranged in the liquid chlorine box; the bottom extending section of the liquid chlorine cavity extends into the machine body; a uniform stirring assembly is in transfer connection into the liquid chlorine cavity; a first cavity is arranged in the machine body positioned under the liquid chlorine cavity; a conversion device is arranged in the first cavity; a guide connection cavity is arranged in the machine body positioned above the right side of the first cavity; a second cavity is arranged in the machine body positioned at the right side of the guide connection cavity; a slide connection groove in left and right extending arrangement is formed in the bottom of the guide connection cavity in a penetrating way; the left side extending tail part of the slide connection groove penetrates through the right side inner wall of the first cavity and is in penetrating arrangement; the right side extending tail part of the slide connection groove penetrates through the left side inner wall of the second cavity and is in penetrating arrangement. The sewage treatment device has the advantages that the structure is simple; the operation is convenient; the service life is prolonged; the chlorine adding efficiency is improved; the workload is reduced; the height regulation can be automatically controlled.