An organometallic compound represented by a following Chemical Formula 1: [Chemical Formula 1] Ir(L A) m (L B) n where in the Chemical Formula 1, L A represents a main ligand, and is one selected from a group consisting of following Chemical Formula 2-1, Chemical Formula 2-2, and Chemical Formula 2-3, L B denotes an ancillary ligand represented by a following Chemical Formula 3, each of m and n denotes a number of the ligands bound to Ir (iridium), and m is 1, 2 or 3, and n is 0, 1 or 2, and a sum of m and n is 3, wherein in each of the Chemical Formulas 2-1 to 2-3, X independently represents one selected from a group consisting of oxygen, sulfur, C 2 and NR, each of R, R 1, R 2-1, R 2-2, R 2-3, R 3-1, R 3-2, R 3-3, R 3-4 and R 3-5 independently represents one selected from a group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, and phosphino, in each of the Chemical Formulas 2-1 to 2-3, two functional groups adjacent to each other among R 2-1, R 2-2 and R 2-3 may be combined with each other to form a ring structure, and two functional groups adjacent to each other among R 3-1, R 3-2, R 3-3, R 3-4 and R 3-5 may be combined with each other to form a ring structure, wherein the ancillary ligand represented by the Chemical Formula 3 is a bidentate ligand, and the bidentate ligand is represented by a following Chemical Formula 4 or a following Chemical Formula 5: wherein in the Chemical Formula 4, each of R 4-1, R 4-2, R 4-3, R 4-4, R 5-1, R 5-2, R 5-3 and R 5-4 independently represents one selected from a group consisting of hydrogen, deuterium, a C1 to C5 linear alkyl group, and C1 to C5 branched alkyl group, wherein the C1 to C5 linear alkyl group or the C1 to C5 branched alkyl group may be substituted with at least one selected from deuterium and a halogen element, two functional groups adjacent to each other among R 4-1, R 4-2, R 4-3 and R 4-4 may be combined with each other to form a ring structure, and two functional groups adjacent to each other among R 5-1, R 5-2, R 5-3 and R 5-4 may be combined with each other to form a ring structure, wherein in the Chemical Formula 5, each of R 6, R 7 and R 8 independently represents one selected from a group consisting of hydrogen, deuterium, C1 to C5 linear alkyl group and C1 to C5 branched alkyl group, wherein the C1 to C5 linear alkyl group or the C1 to C5 branched alkyl group may be substituted with at least one selected from deuterium and a halogen element, two functional groups adjacent to each other among R 6, R 7 and R 8 may combine with each other to form a ring structure, wherein the compound represented by the Chemical Formula 1 includes one selected from a group consisting of following compounds 1 to 370: where in the Chemical Formula 1, L A represents a main ligand, and is one selected from a group consisting of following Chemical Formula 2-1, Chemical Formula 2-2, and Chemical Formula 2-3, L B denotes an ancillary ligand represented by a following Chemical Formula 3, each of m and n denotes a number of the ligands bound to Ir (iridium), and m is 1, 2 or 3, and n is 0, 1 or 2, and a sum of m and n is 3, wherein in each of the Chemical Formulas 2-1 to 2-3, X independently represents one selected from a group consisting of oxygen, sulfur, C 2 and NR, each of R, R 1, R 2-1, R 2-2, R 2-3, R 3-1, R 3-2, R 3-3, R 3-4 and R 3-5 independently represents one selected from a group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, and phosphino, in each of the Chemical Formulas 2-1 to 2-3, two functional groups adjacent to each other among R 2-1, R 2-2 and R 2-3 may be combined with each other to form a ring structure, and two functional groups adjacent to each other among R 3-1, R 3-2, R 3-3, R 3-4 and R 3-5 may be combined with each other to form a ring structure, wherein the ancillary ligand represented by the Chemical Formula 3 is a bidentate ligand, and the bidentate ligand is represented by a following Chemical Formula 4 or a following Chemical Formula 5: wherein in the Chemical Formula 4, each of R 4-1, R 4-2, R 4-3, R 4-4, R 5-1, R 5-2, R 5-3 and R 5-4 independently represents one selected from a group consisting of hydrogen, deuterium, a C1 to C5 linear alkyl group, and C1 to C5 branched alkyl group, wherein the C1 to C5 linear alkyl group or the C1 to C5 branched alkyl group may be substituted with at least one selected from deuterium and a halogen element, two functional groups adjacent to each other among R 4-1, R 4-2, R 4-3 and R 4-4 may be combined with each other to form a ring structure, and two functional groups adjacent to each other among R 5-1, R 5-2, R 5-3 and R 5-4 may be combined with each other to form a ring structure, wherein in the Chemical Formula 5, each of R 6, R 7 and R 8 independently represents one selected from a group consisting of hydrogen, deuterium, C1 to C5 linear alkyl group and C1 to C5 branched alkyl group, wherein the C1 to C5 linear alkyl group or the C1 to C5 branched alkyl group may be substituted with at least one selected from deuterium and a halogen element, two functional groups adjacent to each other among R 6, R 7 and R 8 may combine with each other to form a ring structure,