In a manufacturing of a grasping device that is openable and closable and includes a first jaw having a first hole and a second jaw having a second hole larger than the first hole, the first jaw is arranged in between protruding portions of the second jaw. The second hole is located outside the first hole in a width direction of the grasping device, and a cross-sectional area of the second hole is larger than the first hole. A pin member is inserted through both the first hole and the second hole. The positions of the first jaw and the pin member are adjusted relative to the second jaw to predetermined positions. The pin member is fixed to the second jaw upon positioning the first jaw and the second jaw at the predetermined positions.