The invention belongs to the technical field of sewage treatment, and particularly relates to a device for treating sewage. The device comprises a collecting mechanism for collecting filtered particles, a filtering mechanism for filtering the particles and a driving mechanism, wherein the collecting mechanism is mounted on one side of the filtering mechanism; and the driving mechanism is mounted on the collecting mechanism. During use, the device for treating sewage filter the sewage at different degrees by selecting grid bars with different distances, and can intercept suspended substances and floating substances with different particle sizes by designing the distance between the grid bars to reduce treatment load of subsequent structures and ensure normal operation of equipment; moreover, the device for treating the sewage designed in the invention provides motive power by the filtered particles to realize beneficial effects of automatic filtration and quantitative cleaning of the particles; and a user can filter the sewage layer by layer through the devices for treating the sewage having degressive distances of the grid bars distributed up and down in the equipment.