Abstract: A bonding apparatus according to the present invention relates to a sewing machine (28) which on stitching a connecting flap and a flap to be connected (hereafter referred to as only ‘connected flap’) of one unit, one set of two sheets for a corrugated cardboard box, ensures the folding of the connecting flap and the connected flap, inhibits the blind movement of the position, rectangular in section, of the sheets for the corrugated cardboard box when thread-stitching them, solves the load burdened on a looper mechanism, and provides an appropriate thread-stitching work. The sewing machine (28) comprises a sewing-machine needle mechanism (28b) provided with a sewing-machine needle (28a) and the looper mechanism (28d) having a needle plate (28c).