Provided is a highly reliable solar collecting system. Since a concave minor has a reflection film on a base material on the side opposite to the side of a solar light incoming surface, peeling, breaking and the like are suppressed by protecting the reflection film by the base material, even when a dropping material is brought into contact with the side of the reflection film with impact or accumulated dropped materials are periodically cleaned. As an elliptical mirror has a reflection film on the base material on the side of the solar light incoming surface, even when solar light having large energy enters, the solar light is reflected by the reflection surface before reaching the base material and there is a small possibility of having the base material heated.