To avoid a control error caused by a fluctuation in ground potential due to a high ground current while relaxing a limitation on the degree of freedom in a layout on a circuit board.

The control device includes a circuit board (100) mounted with electrical components. The circuit board has a plurality of ground patterns (140, 142, 144) connected with grounds of the electrical components, and a common connection pattern (146) directly or indirectly electrically connected to a current path to a ground of a power supply. Each ground pattern is individually electrically connected to the common connection pattern, and a ground current flowing out of each ground pattern flows out of the circuit board to reach the ground of the power supply only via the common connection pattern.