emitting apparatus 300 according to embodiment 1 will be described fig1 is a perspective view of illumination apparatus 400 according to embodiment 1 as illustrated in fig1 illumination apparatus 400 includes light emitting apparatus 300 and square surface 410 to be irradiated as described above light emitting apparatus 300 includes illumination lens 100 and light emitting element 200 surface 410 to be irradiated is a square n sided polygon n 4 shaped flat surface light emitting apparatus 300 is disposed in such a manner that surface 410 to be irradiated is perpendicular to central axis ca of illumination lens 100 and the optical axis of light emitting element 200 see fig3 a at this time central axis ca of illumination lens 100 and the optical axis of light emitting element 200 pass through a central part of surface 410 to be irradiated as described above both the horizontal section of incidence surface 110 and the horizontal section of emission surface 120 of illumination lens 100 have a substantially square shape here light emitting apparatus 300 is disposed in such a manner that sides of these two squares and sides of surface 410 to be irradiated are parallel to each other illumination apparatus 400 is used by irradiating surface 410 to be irradiated with light that is emitted from light emitting apparatus 300 light emitting apparatus 300 according to embodiment 1 uniformly irradiates square surface 410 to be irradiated and does not nearly irradiate parts other than surface 410 to be irradiated therefore illumination apparatus 400 can uniformly and effectively illuminate square surface 410 to be irradiated fig1 a is a graph illustrating the light.