An electronic component device includes first and second mount boards, and first, second, and third electronic components. The first electronic component includes a first major surface and a second major surface, and is disposed on the first mount board. The first major surface is positioned closer to the first mount board than the second major surface. The second electronic component includes a third major surface and a fourth major surface, and is disposed on the second mount board. The third major surface is positioned closer to the second mount board than the fourth major surface. The third electronic component includes a fifth major surface and a sixth major surface, and is disposed on the second mount board. The fifth major surface is positioned closer to the second mount board than the sixth major surface. The second major surface directly contacts the fourth and sixth major surfaces, or indirectly contacts the fourth and sixth major surfaces with a bonding layer interposed therebetween.