The electrical device comprises a common device main body having selectively and detachably attached thereto either a variable-voltage power supply device or a high-voltage power supply device. The device main body has: a protruding section that abuts a power supply-side main erroneous attachment prevention section provided in the variable-voltage power supply device and the high-voltage power supply device; a device-side main erroneous attachment prevention section that abuts the power supply-side main erroneous attachment prevention section provided in a low-voltage power supply device and prevents the low-voltage power supply device from abutting an attachment positioning section; and a device-side attachment permitting section that can be combined in a power supply-side auxiliary erroneous attachment prevention section provided in the high-voltage power supply device.