A circuit substrate includes: a base material; and a capacitor layer. The capacitor layer includes a first metal layer that is provided on the base material, a dielectric layer that is provided on the first metal layer, and a second metal layer that is provided on the dielectric layer. The first metal layer includes a first electrode region which is provided on the base material and is exposed from the dielectric layer and to which a first terminal of a capacitor element for supplying current to a circuit part through the capacitor layer is connected. The second metal layer includes a second electrode region in which the second metal layer is exposed and to which a second terminal of the capacitor element is connected.