PURPOSE: To compose speed change structure by which labor for supporting a shift fork shaft on a transmission case can be reduced, and the manufacturing cost can be also reduced.

CONSTITUTION: One side of ends of a shift fork shaft 21 having a firmly set shift fork 22 is inserted into a recess 23 formed on the inside of a transmission case 6, and the other end is attached to the inside of the transmission case 6 together with a supporting member 25 to slidably support this end for equipping the transmission case 6 with the shift fork shaft 22.