An illumination apparatus, comprising: an open-bottom housing body; a light source unit installed within the housing body including a plurality of solid light-emitting elements; a sensor unit installed within the housing body including a wave transmission portion for transmitting energy waves of specified frequency and a wave reception portion for receiving the energy waves reflected from an object, the sensor unit being configured to output a detection signal by detecting the presence or absence of the object within a detection range based on the difference in frequency between the transmitted and received energy waves; a control unit installed within the housing body responsive to the detection signal outputted from the sensor unit for performing a control operation to turn on the light source unit; and, a power source unit installed within the housing body for supplying electric power to the light source unit, the power source unit being arranged outside the detection range of the sensor unit, wherein the sensor unit is provided on the opposite side to the direction of light irradiated from the light source unit whereby the sensor unit is invisible from outside of the housing body, and wherein the sensor unit is arranged so that the light source unit lies within the detection range, the illumination apparatus being characterized in that: the light source unit further includes a light source substrate made of a material capable of passing the energy waves therethrough, the solid light-emitting elements being arranged on the light source substrate. an open-bottom housing body; a light source unit installed within the housing body including a plurality of solid light-emitting elements; a sensor unit installed within the housing body including a wave transmission portion for transmitting energy waves of specified frequency and a wave reception portion for receiving the energy waves reflected from an object, the sensor unit being configured to output a detection signal by detecting the presence or absence of the object within a detection range based on the difference in frequency between the transmitted and received energy waves; a control unit installed within the housing body responsive to the detection signal outputted from the sensor unit for performing a control operation to turn on the light source unit; and, a power source unit installed within the housing body for supplying electric power to the light source unit, the power source unit being arranged outside the detection range of the sensor unit, wherein the sensor unit is provided on the opposite side to the direction of light irradiated from the light source unit whereby the sensor unit is invisible from outside of the housing body, and wherein the sensor unit is arranged so that the light source unit lies within the detection range, the illumination apparatus being characterized in that: the light source unit further includes a light source substrate made of a material capable of passing the energy waves therethrough, the solid light-emitting elements being arranged on the light source substrate. the light source unit further includes a light source substrate made of a material capable of passing the energy waves therethrough, the solid light-emitting elements being arranged on the light source substrate.