Disclosed is a device and method for decreasing interference in a cable bundle. The device includes a plurality of concentration devices, an interference measurer, and a concentration device. Each concentration device accesses an uplink and provides a network service to a terminal through a cable bundle in an access section. An interference measurer is connected between the cable bundle and the terminal. The interference measure is configured to measure an interference signal by measuring a signal transmitted to the terminal through the cable bundle, calculate an interference coefficient for generating a quasi-interference signal, and transmit the same to the concentration devices. The concentration devices is configured to calculate an additional signal for offsetting an interference signal by using the interference coefficient, add the additional signal to the original signal, and transmit the additional signal to the cable bundle.