A lighting device (1) according to an aspect of the invention includes a lighting unit (10); and a mounting unit (11) for mounting the lighting unit (10) to a window frame (109), in which the lighting unit (10) includes a lighting sheet (12) and a frame (13) supporting a peripheral portion of the lighting sheet (12), in which the lighting sheet (12) includes a base material having optical transparency, a plurality of lighting portions having optical transparency which are provided in a first surface of the base material, and a void portion which is provided between the plurality of lighting portions, and in which a part of the side surface of the lighting portion facing the void portion serves as a reflecting surface reflecting light which is incident to the lighting portion.