The invention relates to a flatness checking device, in particular, a flatness checking device for computer case production. The flatness checking device for computer case production has the advantages of saving-time and labor-saving performance, excellent detection effect and reduced error. The flatness checking device for computer case production comprises a work table and the like; supporting plates are symmetrically welded onto the left side and right side of the top of the work table; the work table is provided with a front-and-back moving device; and a first flatness detection device is arranged between the upper parts of the two supporting plates. According o the flatness checking device of the invention, the first flatness detection device and a second flatness detection device are cooperate with each other to detect between a computer case, and therefore, the flatness checking device has the advantages of saving-time and labor-saving performance, excellent detection effect and reduced error.