A flat lamp structure may include a housing; a module in which at least one LED is disposed on a substrate; a reflector which reflects light emitted from the LED to the outside thereof; an inner lens which is disposed in front of the reflector with a predetermined interval to diffuse light emitted from the LED; and an outer lens which is disposed outside the inner lens and coupled to the housing, wherein the reflector has a first reflector part, a second reflector part, and a third reflector part having different optical properties and the first and second reflector parts have a specular reflection characteristic and the third reflector part has a Lambertian reflection characteristic, and reflects the light in all directions with the uniform brightness regardless of a direction to a diffuser surface to form a light emission surface.