To downsize a power smoothing capacitor substrate unit for opening/closing modules configured to convert a low-voltage DC power to AC power to drive a three-phase AC motor. A plurality of unit capacitors (101) being a conductive polymer aluminum electrolytic capacitor are connected between a positive-side first conductive plate (10P0) connected to a positive-side power supply terminal (125P) and a negative-side second conductive plate (10N) connected to a negative-side power supply terminal (124N), and three or more capacitor rows are arranged for each of three pairs of divided power supply terminal blocks (130B) connected to the opening/closing modules (90B) and one or more capacitor rows are arranged between the terminal blocks. Accordingly, ripple currents in a large number of capacitors connected in parallel to each other are equalized to prevent a temperature increase in each capacitor.