A circuit board module includes a first circuit board having a first main surface on which an electronic component that generates heat when the electronic component operates is mounted and a second main surface, a second circuit board having a third main surface on which the first circuit board is mounted and a fourth main surface, and a first thermally-conductive sheet between the first circuit board and the second circuit board. The first circuit board is mounted such that the second main surface faces the third main surface. The first circuit board includes thermally-conductive vias that extend between the first and second main surfaces, the vias being densely distributed in a region near a mounting terminal of the electronic component, filled with a thermally-conductive member, and physically in contact with the first thermally-conductive sheet that covers the third main surface of the second circuit board.