A projector includes a color wheel module and a processing unit. The color wheel module includes a color wheel including multiple color-filtering areas for providing multiple colors of light; a shaft connected to the color wheel for driving the color wheel to spin and including a reflecting surface and a mark; a fixing part disposed corresponding to the shaft; a light transceiver set on the fixing part for emitting light and receiving the light reflected by the shaft; and a vibrator set on the fixing part for vibrating when meeting a vibrating condition to shake off dust on the color wheel, the shaft and/or the light transceiver. The processing unit is coupled to the light transceiver for analyzing a spinning angle of the color wheel according to the light received by the light transceiver.