PURPOSE: To carry out assembling of a negative shedding motion without receiving spring force by setting a spring to a hanger attached to a jack lever and setting a tappet cam in a state where a cam follower of a cam lever is moved backwards.

CONSTITUTION: Jack levers 16, 17 and hangers 21, 22 are attached to a frame 14 and a spring 15 is set between each of stands 20a, 20b and each of the hangers. A leveling lever 3 is rotated against a tensile force of the spring 15 and a cam follower 2A is moved backwards to a position outside the locus of rotation of a tappet cam 1 followed by setting the cam 1 to its rotating shaft 1A. The leveling lever 3 is rotated in the reverse direction and the cam follower 2A of a cam lever 2 is brought into contact with the tappet cam 1 using a tensile force of the spring 15.