An exposing device includes a plurality of light emitting elements, a substrate to which the plurality of light emitting elements are mounted, an optical system that focuses lights emitted by the plurality of light emitting elements, and a holder that holds the optical system. The holder has a substrate abutting surface that abuts against the substrate. The holder includes a base material portion made of metal, and a substrate abutting portion formed integrally with the base material portion. The substrate abutting portion is made of resin having electrical insulation property. The surface abutting surface is formed on the surface abutting portion.