PURPOSE: To perform light speed change operation by providing a tubular change guide coaxially around a bearing body for supporting a change rod and achieving smooth guiding as rotation of the change rod.

CONSTITUTION: A change guide 4 is provided with a guide groove 22 having linear guide groove 21, lower groove 22a and upper groove 22b such that the upper groove 22b will be same height with the guide groove 21 while the guide grooves 21, 22 will be same height. When engaging a guide pin in the guide groove 22 and turning the change lever to move said pin 23 along the upper groove 22b, speed change of advance three speed F3, advance F2 and advance F1 are performed. While when turning the lever 8 to the neutral N position to push down the lever 8 against the spring thus to engage the pin 23 in the lower groove 22a, and turning the lever 8 to back R, backing is performed. In other words, the rod 7 can move smoothly against the guide 4.