A surface illuminating device is provided and includes a plurality of linear light sources, a light-transmissive optical sheet including a luminance-distribution control layer for decreasing unevenness in luminance of light emitted from the linear light sources, and a reflection surface for reflecting the light emitted from the linear light sources. The luminance-distribution control layer includes a plurality of protrusions. In a range of 0≦x≦L/2, protruding directions of some or all the protrusions are inclined such that the protruding directions of the protrusions are located farther from a Z direction, which is an optical axis of a linear light source in an X direction, to the X direction as the protrusions are located farther from the position of x=0 in the X direction, where the X direction represents the arrangement direction of the linear light sources.