A fan detecting apparatus for detecting at least two fans includes a processing unit, at least two airflow switches, and at least two indicating units. The processing unit includes a first terminal configured to output a driving signal, a second terminal configured to receive the driving signal, and a third terminal, the processing unit alarming when the second terminal does not receive the driving signal from the first terminal. The at least two airflow switches are serially coupled between the first and second terminals, monitor airflow from at least two fans in a computer room, and turn on or off according to strength of airflow from the at least two fans. The indicating units are respectively coupled between corresponding airflow switches and the third terminal of the processing unit, and indicate status of corresponding fans according to on or off status of the airflow switches.