A train information managing apparatus comprising: a terminal apparatus that communicates with a train-mounted device and is mounted on a train; and a central apparatus that communicates with the terminal apparatus and the train-mounted device and is mounted on a train, characterized in that in at least one of the terminal apparatus and the central apparatus, a processing system (21A, 21B) that includes a signal processing unit (22A, 22B) is duplicated, the signal processing unit generating a command signal for the train-mounted device and receiving a response signal made in response to the command signal, both of the signal processing units (22A, 22B) that receive a response signal from the train-mounted device transmit, to the respective other of the signal processing units (22A, 22B), information indicating receipt of the response signal via a path that is different from a signal path to the train-mounted device, a first signal processing unit of the signal processing units (22A, 228), when operating as a master, determines that the first processing system including the first signal processing unit is failed in a case when the first signal processing unit receives the information indicating receipt of the response signal from a second signal processing unit of the signal processing units (22A, 228) in a state where the first signal processing unit does not receive the response signal from the train-mounted device, wherein, when a failure is detected, the first signal processing unit stops operating as a master and instructs the second signal processing unit to start operating as a master, and the second signal processing unit of the signal processing units (22A, 228), when operating as a slave, determines that the first processing system including the first signal processing unit is failed in a case when the second signal processing unit receives the response signal from the train-mounted device although the second signal processing unit does not receive the information indicating receipt of the response signal from the first signal processing unit, wherein, when a failure is detected, the second signal processing unit instructs the first signal processing unit to stop operating as a master and starts operating as a master. a terminal apparatus that communicates with a train-mounted device and is mounted on a train; and a central apparatus that communicates with the terminal apparatus and the train-mounted device and is mounted on a train, characterized in that in at least one of the terminal apparatus and the central apparatus, a processing system (21A, 21B) that includes a signal processing unit (22A, 22B) is duplicated, the signal processing unit generating a command signal for the train-mounted device and receiving a response signal made in response to the command signal, both of the signal processing units (22A, 22B) that receive a response signal from the train-mounted device transmit, to the respective other of the signal processing units (22A, 22B), information indicating receipt of the response signal via a path that is different from a signal path to the train-mounted device, a first signal processing unit of the signal processing units (22A, 228), when operating as a master, determines that the first processing system including the first signal processing unit is failed in a case when the first signal processing unit receives the information indicating receipt of the response signal from a second signal processing unit of the signal processing units (22A, 228) in a state where the first signal processing unit does not receive the response signal from the train-mounted device, wherein, when a failure is detected, the first signal processing unit stops operating as a master and instructs the second signal processing unit to start operating as a master, and the second signal processing unit of the signal processing units (22A, 228), when operating as a slave, determines that the first processing system including the first signal processing unit is failed in a case when the second signal processing unit receives the response signal from the train-mounted device although the second signal processing unit does not receive the information indicating receipt of the response signal from the first signal processing unit, wherein, when a failure is detected, the second signal processing unit instructs the first signal processing unit to stop operating as a master and starts operating as a master.