Disclosed is a wiring board on which an optical element is mounted in a state of being sealed by a transparent plate, lens or the like while preventing or reducing the occurrence of condensation or freezing on a surface of the transparent plate, lens or the like. In one embodiment, the wiring board includes: a board body formed with opposed front and back surfaces by stacking of a plurality of ceramic layers (insulating layers); and a plurality of optical element-mounting pads disposed on a bottom surface of a cavity open to the front surface of the board body. The wiring board further includes a heater circuit arranged at the front surface of the board body or an interface of the ceramic layers of the board body along a peripheral side in plan view.