To reduce the number of components, size and weight while preventing breakage of the casing, a high-voltage device provided adjacent to a vehicle component constituting a vehicle includes: a casing housing a high-voltage portion; and a plurality of bolts fastening the casing to an attachment portion to which the casing is attached. The high-voltage device has a first end face at which the casing is in contact with the attachment portion and a second end face opposite to the first end face, and the plurality of bolts are composed of long bolts extending from the second end face to the first endface. The long bolts are each attached to the casing at a position between the vehicle component and the high-voltage portion.