A base configured to carry a light emitting body and to be inserted into a round tube housing, may include: a rectangular portion configured to carry the light emitting body on a first surface of the rectangular portion; and first and second fixing portions configured to extend from first and second long edges of the rectangular portion respectively in a space that a second surface of the rectangular portion faces, such that when the base is inserted into the round tube housing, at least a part of each of the first and second fixing portions presses against the inner wall of the round tube housing, and a first part close to the first long edge and a second part close to the second long edge in the first surface of the rectangular portion press against first and second protrusions on the inner wall of the round tube housing respectively.