A circuit device includes: a heat sink having an upper surface orthogonal to a first direction; a plurality of first partition plates attached to the upper surface and extending in a second direction orthogonal to the first direction; a plurality of second partition plates attached to the upper surface and extending in a third direction orthogonal to the first direction and the second direction; a circuit component; a substrate electrically connected to the circuit component; and a first heat transfer member. The circuit component is housed in a space surrounded by two adjacent first partition plates, two adjacent second partition plates, and the upper surface. The first heat transfer member is disposed between the first partition plate and the circuit component.