A vehicle system comprising: a power transmitter placed at one of at least one charge position; and a vehicle including: a power receiver that wirelessly receives first electric power from the power transmitter, and that outputs second electric power deriving from the first electric power; a capacitor storing the second electric power output by the power receiver such that the capacitor is charged from a first voltage Vc1 to a second voltage Vc2; and a motor driven by the second electric power from the capacitor, wherein the unmanned vehicle automatically travels a distance Dx along a predetermined circulation route from one to a next one of the at least one charge position on the route, characterised in that: the vehicle includes a step-down DC-DC converter circuit that converts a voltage applied to the motor into the drive voltage Vd, and the distance Dx is set such that the first voltage Vc1 is not less than the drive voltage Vd; and the distance Dx satisfies a relationship: Dx ≤ X ⋅ α ⋅ Cc ⋅ Vc 2 2 − Vc 1 2 / 2 ⋅ Id ⋅ Vd where Cc is a capacitance of the capacitor, α is a coefficient not greater than 1 for taking the decrease of the capacitance Cc into consideration, X is a speed of the vehicle, Vd is a drive voltage that drives the motor, and Id is a drive current that drives the motor. a power transmitter placed at one of at least one charge position; and a vehicle including: a power receiver that wirelessly receives first electric power from the power transmitter, and that outputs second electric power deriving from the first electric power; a capacitor storing the second electric power output by the power receiver such that the capacitor is charged from a first voltage Vc1 to a second voltage Vc2; and a motor driven by the second electric power from the capacitor, wherein the unmanned vehicle automatically travels a distance Dx along a predetermined circulation route from one to a next one of the at least one charge position on the route, a power receiver that wirelessly receives first electric power from the power transmitter, and that outputs second electric power deriving from the first electric power; a capacitor storing the second electric power output by the power receiver such that the capacitor is charged from a first voltage Vc1 to a second voltage Vc2; and a motor driven by the second electric power from the capacitor, characterised in that: the vehicle includes a step-down DC-DC converter circuit that converts a voltage applied to the motor into the drive voltage Vd, and the distance Dx is set such that the first voltage Vc1 is not less than the drive voltage Vd; and the distance Dx satisfies a relationship: Dx ≤ X ⋅ α ⋅ Cc ⋅ Vc 2 2 − Vc 1 2 / 2 ⋅ Id ⋅ Vd where Cc is a capacitance of the capacitor, α is a coefficient not greater than 1 for taking the decrease of the capacitance Cc into consideration, X is a speed of the vehicle, Vd is a drive voltage that drives the motor, and Id is a drive current that drives the motor. the vehicle includes a step-down DC-DC converter circuit that converts a voltage applied to the motor into the drive voltage Vd, and the distance Dx is set such that the first voltage Vc1 is not less than the drive voltage Vd; and the distance Dx satisfies a relationship: where Cc is a capacitance of the capacitor, α is a coefficient not greater than 1 for taking the decrease of the capacitance Cc into consideration, X is a speed of the vehicle, Vd is a drive voltage that drives the motor, and Id is a drive current that drives the motor.