A vehicle controller comprising: - a plurality of functional modules; and - signal lines and power lines connected with the functional modules, - wherein one of the sides of the functional module is an interface side provided with signal-line terminals to which the signal lines are connected and power-line terminals to which the power lines are connected, - wherein the plurality of functional modules, as a group, is arranged in such a way that the respective interface sides thereof are adjacent to one another and oriented in the same direction; - wherein the signal lines and the power lines can be attached or detached from one side, characterized in that: each of the interface sides is divided into a first interface region where signal-line terminals to which the signal lines are connected are disposed, and a second interface region where power line terminals to which the power lines are connected are disposed, wherein the first interface regions are disposed in the vicinity of one and the same end and the second interface regions are disposed in the vicinity of the other and the same end, and the plurality of functional modules is divided into a functional module having a switch circuit that is adapted to perform electrical connection with and disconnection from a DC overhead line, a functional module having a charging and discharging circuit that is adapted to perform charging and discharging with a DC voltage, a functional module having an inverter that is adapted to convert a DC voltage into an AC voltage, and a functional module having a contactor that is adapted to perform electrical connection with and disconnection from a load, and the divided functional modules are connected in order of description and utilized as an auxiliary power source apparatus. - a plurality of functional modules; and - signal lines and power lines connected with the functional modules, - wherein one of the sides of the functional module is an interface side provided with signal-line terminals to which the signal lines are connected and power-line terminals to which the power lines are connected, - wherein the plurality of functional modules, as a group, is arranged in such a way that the respective interface sides thereof are adjacent to one another and oriented in the same direction; - wherein the signal lines and the power lines can be attached or detached from one side, characterized in that: each of the interface sides is divided into a first interface region where signal-line terminals to which the signal lines are connected are disposed, and a second interface region where power line terminals to which the power lines are connected are disposed, wherein the first interface regions are disposed in the vicinity of one and the same end and the second interface regions are disposed in the vicinity of the other and the same end, and the plurality of functional modules is divided into a functional module having a switch circuit that is adapted to perform electrical connection with and disconnection from a DC overhead line, a functional module having a charging and discharging circuit that is adapted to perform charging and discharging with a DC voltage, a functional module having an inverter that is adapted to convert a DC voltage into an AC voltage, and a functional module having a contactor that is adapted to perform electrical connection with and disconnection from a load, and the divided functional modules are connected in order of description and utilized as an auxiliary power source apparatus. each of the interface sides is divided into a first interface region where signal-line terminals to which the signal lines are connected are disposed, and a second interface region where power line terminals to which the power lines are connected are disposed, wherein the first interface regions are disposed in the vicinity of one and the same end and the second interface regions are disposed in the vicinity of the other and the same end, and the plurality of functional modules is divided into a functional module having a switch circuit that is adapted to perform electrical connection with and disconnection from a DC overhead line, a functional module having a charging and discharging circuit that is adapted to perform charging and discharging with a DC voltage, a functional module having an inverter that is adapted to convert a DC voltage into an AC voltage, and a functional module having a contactor that is adapted to perform electrical connection with and disconnection from a load, and the divided functional modules are connected in order of description and utilized as an auxiliary power source apparatus.