[Problem] To provide an apparatus for bonding separators in electrical devices wherein even if a unit that performs bonding using ultrasound is used in assembly-line equipment, the amount of space taken up by said equipment can be kept small. [Solution] This invention consists of an apparatus (100) for bonding separators in electrical devices. Said apparatus (100), which is used to bond a pair of separators (40) to each other so as to sandwich an electrode (20), is provided with the following: an oscillator (153) that generates ultrasonic oscillations; a booster (152) that amplifies the generated oscillations; a horn (151) that applies the amplified oscillations to the pair of separators so as to bond said separators to each other; and separator conveyance units (120, 130) that convey the pair of separators to a bonding position where the horn bonds said separators to each other. Either the oscillator, the booster, and the horn are laid out in a plane that is parallel to the direction (X) in which the separators are conveyed and perpendicular to the surfaces of the separators, or the oscillator and the booster are laid out closer to the widthwise centers of the separators than the horn is when seen from a direction that is parallel to the direction in which the separators are conveyed.