Provided are a light source device which includes a light guide plate configured to emit light made incident thereon through one surface thereof, a reflection sheet which has one surface facing the other surface of the light guide plate and is configured to reflect the light made incident on the light guide plate to one surface side of the light guide plate, and an opposite member oppositely disposed to the other surface of the reflection sheet, such that an occurrence of wrinkles and deflection in the reflection sheet may be prevented with a simple configuration, while surely fixing the position of the reflection sheet, and a display apparatus including the light source device.The reflection sheet includes a first reflection sheet piece and a second reflection sheet piece, wherein the first reflection sheet piece is pinched by the light guide plate and the back cover, and the second reflection sheet piece is held by the first reflection sheet piece.