A heat conductive fluid is interposed between an electronic component and a heat sink. The heat conductive fluid serves to enhance the contact between the surface of the electronic component and the opposed surface of the heat sink. The heat conductive fluid also exhibits the property of adsorption between a pair of surfaces based on the fluidity of the heat conductive fluid itself. Although the adsorption allows the slippage of the heat sink along the surface of the electronic component, the adsorption reliably restrains the heat sink from moving in the perpendicular direction perpendicular to the surface of the electronic component. The atmospheric pressure solely acts on the heat sink so as to urge the heat sink against the surface of the electronic component. No excessive urging force is applied to the electronic component. Since the slippage of the heat sink is restrained, the heat conductive fluid can be maintained enough between the heat sink and the electronic component over an enough extent, irrespective of inclination of the surface or vibration of the electronic component. The heat conductive fluid keeps the adsorption acting between the surface of the electronic component and the opposed surface of the heat sink.