Wireless network device and automatically setting configuration method thereof

A wireless network device and an automatically setting configuration method thereof are provided. The device includes a wireless communication module and an operating module. The wireless communication module is used to transmit a test signal to wireless device according to a wireless communication protocol and to receive a response signal transmitted from the wireless device. The operating module is electrically connected to the wireless communication module and is used to calculate a half value of a summation of a shortest transmission time and a longest transmission time. The operating module sets the half value to be an ACK timeout interval of the wireless communication module and analyzes the response signal receiving status during the ACK timeout interval. So as to set the ACK timeout interval to be the longest transmission time or the shortest transmission time, and recalculate the ACK timeout interval.