A light emitting device comprising a light emitter and an optical lens arranged adjacent to the light emitter, the optical lens comprising a first surface, a second surface disposed on the first surface, and a third surface concaved with respect to the second surface toward the first surface, and a plurality of supports extending from the first surface in a first direction toward the light emitter along a circumferential direction of the first surface and disposed adjacent to a circumferential edge of the first surface, wherein the third surface converges in a curved shape symmetrically toward an optical axis (p) of the optical lens, the optical axis (p) passing through a center of the first surface and a center of the third surface, and a predetermined distance is provided between the third surface and the first surface along the optical axis (p), characterized in that the second surface is slanted toward the optical axis (p) as the second surface extends away from the first surface, in that the optical lens further comprises a protruder that is centrally concaved with respect to the first surface and spaced apart from the light emitter, wherein the protruder has two curved portions, each symmetrically curving to the first direction toward the light emitter and then to a second direction opposite to the first direction to substantially meet at the optical axis (p), in that the protruder is formed on the first surface, in that the protruder is configured such that a first light emitted from the emitter, refracted by the protruder and reflected from the second surface is emitted by being refracted by the third surface to proceed along a path B, and a second light emitted from the emitter, refracted by the protruder and reflected from the third surface is emitted by being refracted by the second surface to proceed along a path A, in that a path of the first light refracted by the second surface and a path of the second light refracted by the third surface are mutually in opposite directions, and in that the protruder is adjusted to allow a ratio of light quantity of the light proceeding along the path A and a ratio of light quantity of the light proceeding along the path B to be in the range of 4:1 to 1:4. a plurality of supports extending from the first surface in a first direction toward the light emitter along a circumferential direction of the first surface and disposed adjacent to a circumferential edge of the first surface, wherein the third surface converges in a curved shape symmetrically toward an optical axis (p) of the optical lens, the optical axis (p) passing through a center of the first surface and a center of the third surface, and a predetermined distance is provided between the third surface and the first surface along the optical axis (p), characterized in that the second surface is slanted toward the optical axis (p) as the second surface extends away from the first surface, in that the optical lens further comprises a protruder that is centrally concaved with respect to the first surface and spaced apart from the light emitter, wherein the protruder has two curved portions, each symmetrically curving to the first direction toward the light emitter and then to a second direction opposite to the first direction to substantially meet at the optical axis (p), in that the protruder is formed on the first surface, in that the protruder is configured such that a first light emitted from the emitter, refracted by the protruder and reflected from the second surface is emitted by being refracted by the third surface to proceed along a path B, and a second light emitted from the emitter, refracted by the protruder and reflected from the third surface is emitted by being refracted by the second surface to proceed along a path A, in that a path of the first light refracted by the second surface and a path of the second light refracted by the third surface are mutually in opposite directions, and in that the protruder is adjusted to allow a ratio of light quantity of the light proceeding along the path A and a ratio of light quantity of the light proceeding along the path B to be in the range of 4:1 to 1:4.