The invention relates to a transverse sealing device of a bag making machine, which comprises grooved blocks, fixing rods, return springs, square sleeves, lower seats, linkage rods, splay connecting rods, connecting rods, lever blocks, an upper hot ironing device, a lower hot ironing device, a cylinder and hinge pins. Two connecting holes are respectively disposed at two ends of each splay connecting rod, pin holes are disposed on the connecting rods, and connecting holes I and pin holes I are disposed on the lever blocks. The transverse sealing device is characterized by further comprising compound sleeves and bearings. Two compound sleeves are respectively arranged in each of the connecting holes of the spray connecting rods and each of the pin holes I of the lever blocks, and a bearingis arranged in each of the pin holes on the connecting rods. The transverse sealing device of the bag making machine has the advantage of convenience in maintenance.