A multilayer substrate includes a component mounting electrode, an external mounting electrode, and a heat dissipating unit. The component mounting electrode is connected to an electronic component that is connected to an external structure. The heat dissipating unit is constituted by a plurality of via-conductors partially superposed each other in a stacking direction of the multilayer substrate and disposed continuously between the component mounting electrode and the external mounting electrode. The heat dissipating unit includes communicating portions, each in which one via-conductor is disposed per ceramic layer, and a branching portion in which a plurality of via-conductors are disposed continuously between the communicating portions per ceramic layer. Where the via-conductors of the branching portion and the via-conductor of the communicating portion are adjacent to each other, the positions of the centers of the adjacent via-conductors are separated from each other as viewed from the stacking direction.