To provide a microwave electrodeless lamp of long life, high luminous efficiency, and high brightness.

The microwave electrodeless lamp 10 is structured of an enclosing space 21 made of a non-conductive material with a luminescent substance enclosed inside, a transparent vessel 20 equipped with a depressed part 26 entering inside the sealing space 21 going around an outer periphery, and a conductor 30 of a ring shape fitted along an outer periphery part of the depressed part 26. The microwave electrodeless lamp 10, with microwaves irradiated on it, concentrates electric field components of the microwaves on the center part of the enclosing space 21 by the conductor 30 to emit light in high efficiency.