A lighting module comprising: a first and a second light source (130a, 130b), both of which are disposed opposite to each other; a first case including the first light source; a second case including the second light source; and an optical plate (121, 123) with one side connected to the first case and the other side connected to the second case and on which light from the first and the second light sources (130a, 130b) is incident, wherein the optical plate (121, 123) comprises a first optical plate and a second optical plate and wherein the first and the second optical plates (121, 123) are disposed separately from and opposite to each other, wherein a transmittance of the first optical plate is different from a transmittance of the second optical plate, wherein the first optical plate has a first lumen output and the second optical plate has a second lumen output, and the first lumen output differs from the second lumen output, and wherein a ratio of the first lumen output to the second lumen output is from 4:6 to 2:8, and wherein the lighting module has an empty space inside, the empty space formed by the first case, the second case, the first optical plate and the second optical plate, wherein each of the first and second case (150A, 150B) comprises: a lower case including a base and an extension part extended from one side edge of the base; and an upper case (150a") including a base (151a") and an extension part (152a") extended from one side edge of the base (151a"), wherein the base of the lower case is disposed on the base (151a") of the upper case (150a"), wherein one side of the first optical plate is connected to the extension part of the lower case of the first case, and the other side of the first optical plate is connected to the extension part of the lower case of the second case, and wherein one side of the second optical plate is connected to the extension part (152a") of the upper case (150a") of the first case, and the other side of the second optical plate is connected to the extension part of the upper case (150a") of the second case, wherein each extension part (152a', 152a") extends from one side edge of an inner surface of the respective base (151a', 151a") in a direction perpendicular to the inner surface, and wherein a length of the extension part (152a") of the upper case (150a") is different from a length of the extension part of the lower case. a first and a second light source (130a, 130b), both of which are disposed opposite to each other; a first case including the first light source; a second case including the second light source; and an optical plate (121, 123) with one side connected to the first case and the other side connected to the second case and on which light from the first and the second light sources (130a, 130b) is incident, wherein the optical plate (121, 123) comprises a first optical plate and a second optical plate and wherein the first and the second optical plates (121, 123) are disposed separately from and opposite to each other, wherein a transmittance of the first optical plate is different from a transmittance of the second optical plate, wherein the first optical plate has a first lumen output and the second optical plate has a second lumen output, and the first lumen output differs from the second lumen output, and wherein a ratio of the first lumen output to the second lumen output is from 4:6 to 2:8, and wherein the lighting module has an empty space inside, the empty space formed by the first case, the second case, the first optical plate and the second optical plate, wherein each of the first and second case (150A, 150B) comprises: a lower case including a base and an extension part extended from one side edge of the base; and an upper case (150a") including a base (151a") and an extension part (152a") extended from one side edge of the base (151a"), a lower case including a base and an extension part extended from one side edge of the base; and an upper case (150a") including a base (151a") and an extension part (152a") extended from one side edge of the base (151a"), wherein the base of the lower case is disposed on the base (151a") of the upper case (150a"), wherein one side of the first optical plate is connected to the extension part of the lower case of the first case, and the other side of the first optical plate is connected to the extension part of the lower case of the second case, and wherein one side of the second optical plate is connected to the extension part (152a") of the upper case (150a") of the first case, and the other side of the second optical plate is connected to the extension part of the upper case (150a") of the second case, wherein each extension part (152a', 152a") extends from one side edge of an inner surface of the respective base (151a', 151a") in a direction perpendicular to the inner surface, and wherein a length of the extension part (152a") of the upper case (150a") is different from a length of the extension part of the lower case.