A redundancy device which is configured to communicate with a redundancy opposite device and perform a redundancy execution, the redundancy device includes receivers configured to receive individually HB signals transmitted from the redundancy opposite device, a calculator configured to calculate a number of normal communication paths among communication paths of the HB signals based on a reception result of the receivers, a comparator configured to compare a calculation result of the calculator with a predetermined threshold value, and a changer configured to change the redundancy device from a standby state to an operating state, or change the redundancy device from the standby state to a not-standby state in which the redundancy execution is released, based on the calculation result of the calculator and a comparison result of the comparator.
