A forward-reverse switching lever 14 for switching between forward traveling and reverse traveling is provided to a side of the operation handle 8. An erroneous operation prevention mechanism 40 for restraining reverse shifting of the forward-reverse switching lever 14 when it is operated is provided to the same side of the operation handle 8. An accelerator lever 15 for adjusting the speed of an engine 3 is provided. Operating the forward-reverse switching lever releases position holding of the accelerator lever and causes switchover between forward traveling and reverse traveling. To reduce operational load and prevent erroneous reverse operation, an interlocking mechanism 30 for moving the accelerator lever 15 to low-speed side in conjunction with reverse operation with the forward-reverse switching lever 14 is interposed between the forward-reverse switching lever 14 and the accelerator lever 15. The interlocking mechanism 30 has an interlocking range α, in which the accelerator lever 15 operates in conjunction with operation of the forward-reverse switching lever 14, and a non-interlocking range β, in which a forward-reverse switching device 28 is actuated by operation of the forward-reverse switching lever 14 but the accelerator lever 15 does not operate in conjunction with the operation of the forward-reverse switching lever 14.
