PURPOSE: To provide the sunshine collecting device which has no driving part and is compact by fixedly installing the whole photodetection part which includes a Fresnel lens light collection surface and an optical fiber end part.

CONSTITUTION: A quadrangular pyramid 8 made of optical glass is installed in a pyramid 8 on its pyramid axis and a Fresnel lens 2 made of acrylic resin is mounted at the bottom surface opening part of the pyramid 5. A photodetecting element 6 which is arcuate swelling at the center part and has a ≥0.5 numerical aperture is mounted on the peak part of the pyramid 5. Then an optical fiber bundle 7 of multicomponent glass fibers is connected to the tail end of the photodetecting element 6. The structure is symmetrical about the center axis in the up-down and right-left directions, so even when the sunshine irradiates the pyramid 5 from above or the right or left, the light beam has the same (symmetrical) behavior. More than a half of light irradiating the pyramid within a range of, for example, ±45° from the center axis of the pyramid 5 reaches the photodetecting element 6.