The sheet supply device comprises a sheet stocker including a lifting table mounted for up and down movement with a large number of sheets accumulated in layers thereon which sheets are different in thickness between opposite sides thereof and a paper feed roller for contacting with an uppermost one of the sheets, a string having one end fastened to each of opposite sides of the lifting table corresponding to the opposite sides of the sheets providing the difference in thickness, a first take-up drum or drums located corresponding to the thicker side of the sheets and each having the other end of the string corresponding to the thicker side of the sheets fastened thereto, a second take-up drum or drums located corresponding to the thinner side of the sheets and each having the other end of the string corresponding to the thinner side of the sheets fastened thereto.