A backlight device is disclosed. The backlight device includes a reflection sheet; a frame in contact with the reflection sheet; and a light guiding plate surrounded by the frame; wherein the frame comprises: a first surface in contact with the reflection sheet, a second surface spaced apart from the reflection sheet, at least one groove configured to secure a light emitting element, and a heat dissipation channel in at least one of the first surface and the second surface of the frame, wherein the heat dissipation channel is located at periphery of the groove.