The invention discloses a tower-type horizontal flow settling device. The device comprises multiple horizontal flow guide units, wherein each horizontal flow guide unit is a semi-sealed cavity which is formed by two long-strip-shaped vertical flow guide plates and two long-strip-shaped oblique flow guide plates and has a lower opening, and a sludge removal port is formed by each vertical flow guide plate and the corresponding oblique flow guide plate which are adjacent vertically; multiple partition boards are arranged between the horizontally adjacent flow guide units, each partition board is connected with the two adjacent flow guide units, and a sludge settling channel is formed between every two adjacent partition boards. To-be-treated sewage and settled sludge are subjected to interval separation through the horizontal flow guide units, flowing of sewage cannot influence the settled sludge, secondary interference of the sewage to the settled sludge is avoided, suspending matter settles once to form sludge to be discharged from sludge removal grooves, and the settling efficiency of the suspending matter in the sewage is improved.