PURPOSE: To produce a tractor at a low cost by forming a clutch gear for normal rotation and a clutch gear for reverse rotation into the same shapes in a normal/reverse rotation switching gear mechanism for a tractor.

CONSTITUTION: In the front side and the rear side in the axial direction of a clutch metal 3, which is rotated integrally with a clutch shaft 1 and is provided with a clutch ring 2 freely movable in the axial direction by means of a shifter on the outer circumference, same-shaped clutch gears 9, 10, each of which is provided with a clutch claw part 4 to which the clutch ring 2 can be geared, a ring groove part 5 with the fixed width, and a gear part 8 to which a transmission gear 6 or 7 is always geared, are symmetrically arranged freely rotationally.