The invention provides a cable conveying device for horizontal wells. A horizontal well comprises a vertical well section and a horizontal well section connected with the vertical well. The cable conveying device comprises a conveying pipeline whose one end is positioned inside the vertical well section and the other end extends to a free end of the horizontal well section; a traction member is slidingly arranged inside the conveying pipeline and is connected with the cable so as to pull the cable into the horizontal section. The technical solution of the present invention can solve the problem in the prior art that it is difficult to send the cable to the horizontal well section of the horizontal well.