An optical module includes an optical element, a first substrate, on a first principal plane of which the optical element is mounted, a holding member disposed on a second principal plane of the first substrate, an optical fiber inserted into a through hole of the holding member, a holding substrate with an opening, a wall surface of which is in contact with an outer peripheral surface of the holding member, an interconnecting substrate connecting the first substrate and the holding substrate, a side surface substrate, an end portion of which is connected to the holding substrate and on which an electrode is disposed, and a signal cable, a distal end portion of which is bonded to the electrode of the side surface substrate.