Provided are a reflection sheet which is capable of, when light sources, and the like are disposed on one side surface side of a light guide plate, preventing the reflection sheet from coming into contact with the light sources, and the like at a central part of the one edge thereof, and a light source device and a display apparatus. A reflection sheet which is oppositely disposed to the other surface of a light guide plate for emitting light made incident on one side surface from one surface thereof, and reflects the light made incident on the light guide plate to the one surface side of the light guide plate, includes a cutout part provided at a central part of one edge of four sides of the rectangular reflection sheet, and the reflection sheet is arranged so that the one edge is disposed on one side surface side of the light guide plate.