A vehicle comprising: a power supply; a plurality of motors (M1, M2); a plurality of inverters (14A, 14B) performing electric power conversion between said power supply and said plurality of motors (M1, M2); an insulating resistor (Z1, Z2, Z3) for externally, electrically insulating an electric conduction path connecting said power supply, said plurality of motors (M1, M2), and said plurality of inverters (14A, 14B); and a detector connected to said insulating resistor (Z1, Z2, Z3) via said electric conduction path and configured to perform a determination process to determine whether said insulating resistor (Z1, Z2, Z3) is defective, based on how a determination signal varies in potential, to detect whether said insulating resistor (Z1, Z2, Z3) is defective, said determination signal varying in potential as said insulating resistor (Z1, Z2, Z3) has a reduced resistance value, and also varying when said plurality of inverters (14A, 14B) have operating frequencies with a difference smaller than a predetermined value; the vehicle being characterized by comprising a controller, the controller comprising: a determination unit configured to determine whether the detector is performing the determination process, and a control unit (200A, 200B, 300) configured to control said operating frequencies of said plurality of inverters (14A, 14B) in accordance with a result provided by said determination unit, wherein when said determination process is currently not performed, said control unit (200A, 200B, 300) is configured to perform random control to arbitrarily vary each of said operating frequencies of said plurality of inverters (14A, 14B), and wherein when said determination process is currently performed, said control unit (200A, 200B, 300) is configured to perform limitative control to restrict said random control to allow said plurality of inverters (14A, 14B) to have said operating frequencies with limited variation to prevent said operating frequencies from having a difference smaller than said predetermined value. a power supply; a plurality of motors (M1, M2); a plurality of inverters (14A, 14B) performing electric power conversion between said power supply and said plurality of motors (M1, M2); an insulating resistor (Z1, Z2, Z3) for externally, electrically insulating an electric conduction path connecting said power supply, said plurality of motors (M1, M2), and said plurality of inverters (14A, 14B); and a detector connected to said insulating resistor (Z1, Z2, Z3) via said electric conduction path and configured to perform a determination process to determine whether said insulating resistor (Z1, Z2, Z3) is defective, based on how a determination signal varies in potential, to detect whether said insulating resistor (Z1, Z2, Z3) is defective, said determination signal varying in potential as said insulating resistor (Z1, Z2, Z3) has a reduced resistance value, and also varying when said plurality of inverters (14A, 14B) have operating frequencies with a difference smaller than a predetermined value; the vehicle being characterized by comprising a controller, the controller comprising: a determination unit configured to determine whether the detector is performing the determination process, and a control unit (200A, 200B, 300) configured to control said operating frequencies of said plurality of inverters (14A, 14B) in accordance with a result provided by said determination unit, wherein when said determination process is currently not performed, said control unit (200A, 200B, 300) is configured to perform random control to arbitrarily vary each of said operating frequencies of said plurality of inverters (14A, 14B), and wherein when said determination process is currently performed, said control unit (200A, 200B, 300) is configured to perform limitative control to restrict said random control to allow said plurality of inverters (14A, 14B) to have said operating frequencies with limited variation to prevent said operating frequencies from having a difference smaller than said predetermined value. a determination unit configured to determine whether the detector is performing the determination process, and a control unit (200A, 200B, 300) configured to control said operating frequencies of said plurality of inverters (14A, 14B) in accordance with a result provided by said determination unit, wherein when said determination process is currently not performed, said control unit (200A, 200B, 300) is configured to perform random control to arbitrarily vary each of said operating frequencies of said plurality of inverters (14A, 14B), and wherein when said determination process is currently performed, said control unit (200A, 200B, 300) is configured to perform limitative control to restrict said random control to allow said plurality of inverters (14A, 14B) to have said operating frequencies with limited variation to prevent said operating frequencies from having a difference smaller than said predetermined value.