An illuminating device includes: a lamp device that includes a lamp body, which is a light source, and a concave reflector for reflecting light emitted from the lamp body; and a lens member that has a planar optical surface and a nonplanar optical surface opposite to the planar optical surface and is provided on an emission side of the lamp device. In the illuminating device, the lens member is arranged such that a normal line of the planar optical surface is slightly inclined at a predetermined angle with respect to an optical axis of the lamp device. The lens member is arranged such that light beams substantially parallel to the optical axis are incident on the planar optical surface, and a filter that reflects at least one of an ultraviolet ray and an infrared ray is provided on the planar optical surface.
