An optical module includes a driving unit, a first color wheel, a second color wheel, a first electromagnet, a plurality of first magnets and a polarity control unit. The driving unit has a rotating shaft. The first color wheel is fixed on the rotating shaft. The second color wheel is freely disposed on the rotating shaft. The first electromagnet is disposed on the first color wheel and the first magnets are disposed on the second color wheel. The driving unit drives the first color wheel to rotate, such that the first electromagnet rotates along with the first color wheel. The polarity control unit controls a direction of current flow in the first electromagnet to control a polarity of the first electromagnet, such that the first electromagnet attracts one of the first magnets during rotation to drive the second color wheel to rotate along with the first color wheel.