A connection structure includes: a circuit breaker connected to a power cable through which high-voltage power is supplied; a high-voltage device box accommodating the circuit breaker; a main transformer configured to transform a voltage of the high-voltage power and provided under the floor of the car; a first connector device electrically connected to the circuit breaker and provided at a dividing wall of the high-voltage device box; a second connector device electrically connected to the main transformer and provided at a dividing wall of the main transformer; and a high-voltage cable covered with an insulating coating and having both end portions to which cable connector portions are respectively attached, wherein the high-voltage cable connects the first connector device and the second connector device in such a manner that the cable connector portions respectively fit and are connected to the first connector device and the second connector device.