<；P>；PROBLEM TO BE SOLVED: To provide a cooling device efficiently cooling a heat source and effectively using waste heat after cooling, to provide a lighting system using the cooling device, to provide a plant raising device using the lighting system, and to provide a cooling method. <；P>；SOLUTION: This cooling device is such that a cooling unit 50 cooling a heat source such as a light source unit 30 has an inlet pipe 51 and an outlet pipe 52, the inlet pipe 51 is communicated with an outdoor intake vent 11 and an indoor intake vent 12 each intake air from the outside and inside, and the outlet pipe 52 is communicated with an outdoor exhaust vent 21 and an indoor exhaust vent 22 each exhausting air to the outside and inside. Furthermore, an intake changing valve 13 changes for intake air either the outdoor intake vent 11 or the indoor intake vent 12, and an exhaust changing valve 23 changes for exhaust air either the outdoor exhaust vent 21 or the indoor exhaust vent 22. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
