PURPOSE: To prevent the burning of a clutch due to the forward/backward switching by decreasing an engine speed with a clutch pretective means in operation of a forward/backward switching mechanism of a working vehicle, in which the traveling speed exceeds a set value.

CONSTITUTION: A forward/backward lever is connected with the operational circuit 22 of an operational valve V through a forward/backward switching means 23 composed of a microcomputer C and a pair of switches S1, S2 for detecting the operational position, thus constituting a forward/backward switching mechanism 25 for selectively inputting the respective switches FC, RC for forward/backward movement. In this case, there is provided a means 28 on the microcomputer C for detecting the operation of the forward/backward switching mechanism 25. When, the forward/backward switching mechanism 25 is operated in the condition that the traveling speed of the working vehicle exceeds the set value, the engine E is decreased with a clutch protective means 34 mounted on the microcomputer C.