A guiding device and a projector comprising the same are provided. The projector comprises a blower and a bulb. The blower is used for cooling the bulb. The guiding device is disposed between the blower and the bulb, and comprises a body and a flapper. The body of the guiding device is formed with a first outlet and a second outlet. The first outlet and the second outlet are adapted to guide the blower to form a first airflow and a second airflow, respectively. The flapper is disposed in the second outlet and moves along a direction of gravity to partially cover the second outlet to force the second airflow to flow towards a portion of the bulb away from the direction of gravity.