To enhance heat radiating performance of a LED unit while making a system thin and compact, in a LED lighting system wherein the LED unit can be freely exchanged.

This LED lighting system 1 is provided with a LED unit 2 and a unit holding body 3 to which this LED unit is mounted, the LED unit 2 is provided with a housing to store a LED or the like and a connector 41a to feed to the LED, and the unit holding body 3 is equipped with a front cover 31 and an arm part 32 for detachably holding the LED unit 2 so that a part of the housing 20 of the LED unit forms the appearance of the system and a connector 41b connected to a connector 41a and a power supply. Since a part of the housing 20 of the LED unit forms a part of the appearance of the system, the system can be made thin and compact by cutting down the number of members covering the LED units 2, and since a part of the housing 20 of the LED unit directly touches the outside air, heat radiating performance is enhanced.