A fan detecting apparatus for detecting operation of at least two fans includes at least two airflow detecting units with two signal transmitting terminals, a judging unit with at least one judging terminal, and at least two identity indicating units electrically coupled to the corresponding at least two airflow detecting units respectively. The airflow detecting units detect airflow of the fans, and output control signals to corresponding identity indicating units when airflow from corresponding fans is no longer detected. Each of the identity indicating units has an identity code corresponding to a fan which is electrically coupled to the airflow detecting unit, and transmits the identity code to the judging terminal of the judging unit when it receives the control signal. The judging unit indicates which of the fans is no longer producing detectable airflow according to the identity codes received at its judging terminal.