A living body stimulator for stimulating a living body through a light irradiation from a light source, comprising: one or more moveable LED irradiators as light irradiators, wherein each LED irradiator comprise one or more LEDs serving as the light source and a light transmissive panel provided in an irradiation direction of each LED, a temperature sensor serving as a temperature detection unit disposed in an inner space of the LED irradiator; and wherein the living body stimulator further comprises: a brightness control unit for variably controlling a brightness of said light source by receiving a detection output from said temperature detection unit, said brightness control unit extending an irradiation period of said light source in accordance with a decrease in the brightness of said light source when the brightness of said light source has been decreased through control, characterized in that said temperature sensor, for detecting a temperature of an irradiation surface of the light transmissive panel contactable: with the living body, comprises a thermosensitive part, which abuts against an inner surface of said light transmissive panel provided on a side opposite to said irradiation surface, wherein the brightness control unit is adapted to control the brightness of said light source such that the temperature of said irradiation surface becomes not higher than 42° C. one or more moveable LED irradiators as light irradiators, wherein each LED irradiator comprise one or more LEDs serving as the light source and a light transmissive panel provided in an irradiation direction of each LED, a temperature sensor serving as a temperature detection unit disposed in an inner space of the LED irradiator; and wherein the living body stimulator further comprises: a brightness control unit for variably controlling a brightness of said light source by receiving a detection output from said temperature detection unit, said brightness control unit extending an irradiation period of said light source in accordance with a decrease in the brightness of said light source when the brightness of said light source has been decreased through control, characterized in that said temperature sensor, for detecting a temperature of an irradiation surface of the light transmissive panel contactable: with the living body, comprises a thermosensitive part, which abuts against an inner surface of said light transmissive panel provided on a side opposite to said irradiation surface, wherein the brightness control unit is adapted to control the brightness of said light source such that the temperature of said irradiation surface becomes not higher than 42° C. a brightness control unit for variably controlling a brightness of said light source by receiving a detection output from said temperature detection unit, said brightness control unit extending an irradiation period of said light source in accordance with a decrease in the brightness of said light source when the brightness of said light source has been decreased through control, characterized in that said temperature sensor, for detecting a temperature of an irradiation surface of the light transmissive panel contactable: with the living body, comprises a thermosensitive part, which abuts against an inner surface of said light transmissive panel provided on a side opposite to said irradiation surface, wherein the brightness control unit is adapted to control the brightness of said light source such that the temperature of said irradiation surface becomes not higher than 42° C.