This daylighting device (10) is used by being pasted onto a window frame (110) supporting an existing window glass (100), and comprises: a light-transmissive first base material (11); a first spacer (12) provided at an external edge portion of one surface (11a) of the first base material (11), and to be pasted onto the window frame (110); and a daylighting member (13) provided on one side of the surface (11a) of the first base material (11). The daylighting member (13) comprises a light-transmissive second base material (14), and a plurality of light-transmissive protrusion-shaped daylightingportions (15) provided to be adjacent to one another on one side of a surface (14a) of the second base material (14).