To provide a device for taking in light into a room of a building as a measure against restrictions that a storage room or a basement with a window located completely or partially under the surrounding land has in utilization as compared with one above the land, apart from psychological factors affected by general lack in additional energy consumption and sunlight.

A casing 3 is provided, which is fitted to a wall 5 of a room 42 for letting in light. An outside end area 38 of the end area of the casing 3 is within an area of a land surface 4. A device for reflecting light or guiding light is arranged in the casing 3, which is structured so as to guide light from the outside end area of the casing 3 into the room 42 to let in light into.