A dust-proof structure of a projector includes a color wheel module, an air diversion panel, and a circuit board. The color wheel module has a motor and a color wheel. The motor drives the color wheel by an axle to rotate. The air diversion panel is located on the circuit and positioned under the motor. The air diversion panel has an opening, a dust exit, and a dust collecting trough. The opening is positioned between the dust exit and the dust collecting trough. The circuit board has a sensor, which is placed in the opening of the air diversion panel. The dust exit and the dust collection trough of the air diversion panel prevent the sensor from dust aggregation.