Lighting apparatus

A lighting apparatus comprising:

• a light source unit configured to emit light in a forward direction;
• a plate coupled to a back side of the light source unit and including a through hole formed at a center of the plate;
• a holder interposed between the light source unit and the plate and including an accommodation groove which faces the through hole, wherein the accommodation groove of the holder includes:
• a first sidewall and a second sidewall which face each other;
• and
• a third sidewall and a fourth side wall which are connected between the first sidewall and the second sidewall and face each other,
• wherein the accommodation groove includes a first width which extends in a first direction from the first sidewall to the second sidewall, and a second width which extends in a second direction which intersects with the first direction and which extends in the second direction from the third sidewall to the fourth sidewall, and
• a socket that includes a body to accommodate in the accommodation groove of the holder and a plurality of protruding steps that selectively protrude outward from the body and insert inwardly from the body based on location of the protruding steps with respect to different ones of the sidewalls, wherein the protruding steps move to insert inwardly from the body when the protruding steps contact the third sidewall and the fourth sidewall,
• the first width between the first sidewall and the second sidewall is greater than a diameter of the through hole of the plate, and the second width between the third sidewall and the fourth sidewall is less than the diameter of the through hole of the plate.