A wireless communication device and a controlling method thereof. The wireless communication device performing wireless communication includes a transceiver for transmitting and receiving data externally, and a controller for processing the data received from the transceiver, the wireless communication device operating as a slave that is connected to a master, the controller receiving a polling data addressed to the device from a master through the transceiver, and temporarily stopping the operation of the transceiver during a sleep period which is determined according to the number of other slaves connected to the master. Since the wireless communication device operated as an active slave can stop its data transmission/reception during a communication standby period, i.e., until the beginning of the next polling slot, the power consumption can be considerably reduced without affecting the communication itself.