Abstract: A surgical instrument for suturing tissue with metal staples includes an anvil unit which has two elongated jaws aligned with each other and having inner surfaces facing each other and formed with longitudinal guiding grooves for a staple. The front ends of the jaws carry anvils for bending the tips of the staples, said anvils being shaped as curved needles, having tips facing each other and formed with longitudinal grooves which are extensions of said guiding grooves of the jaws. The jaws can be releasably connected to each other in a position in which the longitudinal grooves of the jaws are approximately parallel to each other. A detachable staple-driving unit has a frame mounted on the jaws, provided with grooves for a staple and a staple driving member with a lever for operating the same.