An accelerator pedal system includes a pedal control unit that receives a vehicle speed signal and a signal from a switch, and compares the two signals. If the vehicle speed exceeds a preselected speed, the pedal control unit outputs a control signal to control a reaction force of an accelerator pedal on the basis of the preselected speed and a selected mode. The system also includes a reaction device that receives the control signal and controls the accelerator pedal according to the selected mode. The reaction device includes an actuator for generating power on the basis of the control signal, a power delivery unit for selectively transmitting the power generated by the actuator, and a wheel for receiving the power from the power delivery unit and transmitting the power to the accelerator pedal.