The invention relates to a square floor drain for transverse drainage, which can effectively solve and thoroughly eliminate the problem of seepage dripping hidden dangers caused by a floor drain pipe passing through a floor slab. The structure of the square floor drain for the transverse drainage is that: a square shell is connected with a flat bottom to form a square box which has a bottom but no cover; a transverse drain pipe is positioned at one end of the square box; in the square shell, overflow plates are arranged on the two sides of a symmetry axis; the top surfaces of the overflow plates are positioned on the top surface of the square box; a drain groove is formed between two overflow plates; the drain groove is communicated with the transverse drain pipe; a guide plate is arranged outside each overflow plate; the top surfaces of the two guide plates are flush with the top surface of the square shell therebetween to form a rectangular frame; a top cover is arranged on the rectangular frame; drain grooves are formed between the bottom surface of the top cover and the overflow plates; the drain grooves are communicated with the transverse drain pipe; an uplink water channel is formed between each of the overflow plates and each of the two guide plates; a downlink water channel is formed between each of the two guide plates and the square shell; and a grate is arranged ina wastewater inlet and is connected with the top cover integrally. The square floor drain for the transverse drainage has a good using effect, effectively prevents indoor water seepage, is easy to splice with floor ceramic chips and contributes to constructing.