A circuit board includes a metal pattern layer, a thermally conductive plate, an electrically insulating layer, and at least one electrically insulating material. The thermally conductive plate has a plane. The electrically insulating layer is disposed between the metal pattern layer and the plane and partially covers the plane. The electrically insulating material covers the plane where is not covered by the electrically insulating layer and touches the thermally conductive plate. The electrically insulating layer exposes the electrically insulating material, and a thermal conductivity of the electrically insulating material is larger than a thermal conductivity of the electrically insulating layer.