The present invention is achieved with the object of providing an illumination system formed of an LED light emitting body and a socket which can appropriately release heat from LED chips. This object is achieved in the following manner. A heat conducting layer 12 made of diamond is provided on a substrate 11, and on top of this, a conductive layer 13 having a predetermined pattern is formed. LED chips 16 are mounted in predetermined positions on the conductive layer 13. Terminals of the conductive layer 13 and electrodes of the LED chips 16 are connected to each other. A connector part 14 for the connection to a socket is provided in an end portion of the substrate 11. The heat conducting layer 12 on the connector part 14 makes thermal contact with the heat conducting layer provided on the inner surface of the opening of the socket. A current is supplied to respective LED chips 16 through the conductive layer 13 from the socket, and respective LED chips 16 emit light. Heat that is generated in the LED chips 16 is released to the outside of the illumination system from the socket through the conductive layer 13, the heat conducting layer 12 and the connector part 14. As a result of this, an increase in the temperature of the LED chips 16 can be prevented, and an LED illumination system that emits a large amount of light can be formed.