An electronic device is immersed in a coolant in a cooling apparatus, and directly cooled. The electronic device is configured to be housed in housing parts of the cooling apparatus, and includes a metal board held with a pair of board retainers disposed in the housing part, storage units attached to a first surface of the metal board and a second surface opposite the first surface, and a backplane including connectors for electrically connecting the respective storage units, attached orthogonally to the first surface of the metal board, and the second surface opposite the first surface. The metal board includes a primary member including cuts in a width direction for fixing support plates that support the storage units to the primary member, and a secondary member includes pawls inserted into slits in the backplane, and fixed to the primary member. The support plates include holes for passage of the coolant.