An illuminating device includes a
light source including a light-emitting element, an
electrode electrically connected to the light-emitting element, and a heat
radiation terminal electrically isolated from the light-emitting element; and a multilayer substrate including a plurality of insulating
layers, a plurality of
metal layers, an electrically conducting interlayer contact portion, and a heat-conducting interlayer contact portion. The insulating
layers include all insulating layer having a
mount surface on which the
light source is mounted with the
electrode and the heat
radiation terminal therebetween. The
metal layers include an electrically conducting
metal layer electrically connected to the
electrode and disposed so as to be separated from the
light source by the insulating layer having the
mount surface and an electrically isolated metal layer electrically isolated from the other metal layers and disposed most distant from the
mount surface of all the metal layers. The electrically conducting interlayer contact portion electrically connects the electrode to the electrically conducting metal layer. The heat-conducting interlayer contact portion connects the heat
radiation terminal to the electrically isolated metal layer.