Provided is a substrate unit configured to improve heat dissipation efficiency while preventing workability from degrading at the time of assembly. A substrate unit includes: a substrate that has one surface on having a conductive pattern, and includes an opening; a conductive member that includes a main portion is fixed to the other surface of the substrate, and at least one terminal of an electronic component is electrically connected via the opening; and a heat dissipation member is fixed to a surface of the conductive member opposite a substrate side surface thereof, wherein the conductive member is provided with an extension portion that extends from the main portion of the conductive member and to which an external device is to be electrically connected, the extension portion intersecting a plane that extends along the heat dissipation member.