A fan motor control device for controlling the soft start of a fan motor is disclosed. The fan motor control device comprises a converter, a starting capacitor, and a controller. The converter sends out a control signal to the controller based on an input pulse-width modulation signal. The starting capacitor is coupled between a voltage source terminal and a controlled terminal of the controller. Thereby, based on an input voltage to the controlled terminal, the controller controls the soft start of the fan motor. For the soft start period, the magnitude of the input voltage is determined by the base working voltage outputted via the voltage source terminal. While for normal operation, based on the input voltage to the controlled terminal, the controller controls the speed of the fan motor, with the magnitude of the input voltage determined by the control voltage outputted by the converter.