To provide a sunlight sensor which can be simplified in handling, assembly, and positioning without limiting the degree of freedom for designing an artificial satellite.

An incident port 2 of sunlight is opened in a cover 1, and a plurality of optical fiber cables 4 receive sunlight introduced through the incident port 2 and transmit it to a sunlight detection part. An optical fiber positioning ring 3 arranges each of end faces of the plurality of optical fiber cables 4 in a half-spherical shape and holds them so that each of end faces of the plurality of optical fiber cables 4 crosses an incident axis of sunlight introduced through the incident port 2 at a right angle. An optical fiber protective cap 5 and an optical fiber protective sleeve 6 bundle the plurality of optical fiber cables 4 and cover them.