A heat-radiating structure of an electronic card unit is compact and reinforces a printed circuit board while improving heat radiation efficiency. Card unit 6 has dual function reinforcing plate-heat dissipaters 17 and 18 at the upper and lower edges of a printed circuit board 12 on which a heat-generating component 19 is mounted. Heat generated by component 19 is conducted to the reinforcing plate-heat dissipaters by passing a fluid in a heat pipe 21, a heat-conducting sheet 31 or a heat radiation circulation pipe 41 to be removed into the air. The reinforcing plates-heat dissipaters 17 and 18 are formed with a plurality of air vents 17a and 18a.