The invention discloses a timber cutting device, and relates to the field of timber processing. The timber cutting device is characterized by comprising a base, a supporting frame and a cutting device body, timber fixing clips are arranged on the base, the supporting frame is connected with the upper surface of the base, a slide groove is formed in the side face of the supporting frame, the cutting device body is arranged in the slide groove, a push rod motor is arranged in the slide groove and connected with the bottom face of the cutting device body, the cutting device body comprises a rectangular frame, a first cutting part and a second cutting part, scale markers are arranged on the rectangular frame, two installation grooves are formed in the corresponding positions of the inner wall of the rectangular frame, a plurality of stop pieces are arranged in the installation grooves, a left installation plate and a right installation plate are connected between the installation grooves, the first cutting part is arranged on the side face of the left installation plate, and the second cutting part is arranged on the side face of the right installation plate. The timber cutting device is simple in structure, small in size and high in cutting efficiency.