This light source unit has a hole for a suspension bolt to pass through, and is removably attached to a fixture main body attached to a ceiling member by means of a suspension bolt passed through the hole. The light source unit is provided with: an LED substrate to which a plurality of LEDs are mounted; an attachment member for attaching to the fixture main body the LED substrate in a manner so that the LED substrate is disposed between the plurality of LEDs and the fixture main body; and a power source device that supplies lighting electrical power to the plurality of LEDs. The attachment member has a housing section at which the power source device and at least a portion of the suspension bolt are disposed at a site facing the fixture main body. The power source device is disposed at a position that does not interfere with the suspension bolt within the housing section in the state of the light source unit being attached to the fixture main body.
