To provide the speed control structure of a motor-driven vehicle capable of preventing noise from acting on electric signals for controlling speed and eliminating the danger of disconnecting a harness or the like for instance for sending the electric signals.

This speed control structure of the motor-driven vehicle is provided with a speed adjustment means (accelerator lever) provided on the front position of a seat where a crew member sits for adjusting the speed by displacement, a displacement electric signal conversion means (displacement electric signal converter) 53 for converting the displacement amount of the speed adjustment means to the electric signals, a main controller 54 for controlling the speed corresponding to the electric signals from the displacement electric signal conversion means 53 and a main controller case 5 provided on the lower position of the seat for housing the main controller 54. In this case, the main controller case 5 is constituted of a metallic one and the displacement electric signal conversion means 53 is provided inside the main controller case 5.