To have an advantage on an installation space by a switching rod guided in a very narrow space and individually operated, and to easily handle a switching module in installing it by previously assembling and inserting the switching module into a gear transmission.

The switching model 1 is provided with a rolling bearing 4, and a roller body 10 of the rolling bearing 4 is arranged in a square receiving part 11 of a casing 2 so that the roller body 10 extends in parallel with respect to a longitudinal direction axis 14 of the switching model 1. A lock device 5 is arranged so as to deviate with respect to the rolling bearing 4 along an axial direction. Rock members 13 corresponding to the respective switching rods 6a to 6d are provided in the lock device.