An electronic apparatus, a wireless input device and a control method thereof are provided. The wireless input device includes a wireless signal receiver, a control chip, and a wireless signal transmitter. The wireless signal receiver receives a radio frequency signal. The control chip is activated according to the radio frequency signal and generates operation power according to the radio frequency signal. The control chip generates input information by detecting an input operation on an input interface based on the operation power. The wireless signal transmitter transmits the input information to an external electronic apparatus based on the operation power.