To provide a dental shadowless lamp which can automatically follow a desired position relative to the oral cavity position of a patient without being handled by an operator, and can be automatically turned on or off, which therefore can be handled and operated sanitarily.

The shadowless lamp 5 for illuminating the inside of oral cavity of the patient includes on its surface: a temperature sensor 11 (for detecting the intraoral temperature of the patient); a metal sensor 12 (for detecting an instrument when the operator performs a dental treatment); and a distance sensor 13 (for detecting a distance to the face of the patient). The shadowless lamp 5 is automatically moved close to the oral cavity of the patient and turned on based on the detection signals from the above sensors.