A circuit assembly is provided. The circuit assembly includes: a first bus bar and a second bus bar that are part of a power circuit; and a control board to which a control circuit configured to control current flow in the power circuit is mounted, the circuit assembly including: a semiconductor switching element including a drain terminal and a source terminal that are connected to the first bus bar and the second bus bar, respectively, and a gate terminal configured to receive input of a control signal from the control circuit configured to control current flow in the power circuit; and a third bus bar configured to electrically connect the gate terminal and the control board.