The electronic parts (CPU element (2a), capacitor (2b) and coil element (2c)) with different height are installed on the printed circuit board (1). A heat-absorbing element (3) are arranged at the upper side of the printed circuit board (1) with the mode of contacting the upper surface of the CPU element (2a) with lowest height and contacting the side surface of the coil element (2c). The heat-absorbing element (3) is formed with a flow circuit (4) for circulating the cooling medium. The heat generated in the CPU element (2a) is transferred to the cooling medium in the flow circuit (4) from the upper surface through the heat-absorbing element (3), and the heat generated in the capacitor (2b) and the coil element (2c) is transferred to the cooling medium in the flow circuit (4) from the side surface through the heat-absorbing element (3).