According to one embodiment, a liquid crystal display device includes a liquid crystal panel and a backlight device. The backlight device includes a case with a bottom plate and a side plate, a light guide on the bottom plate, and a light source device. The light source device includes a wiring substrate and a light-emitting element on the wiring substrate. The wiring substrate includes a mounting portion on which the light-emitting element is mounted, a connection wiring portion on a back surface side of the bottom plate, and a joint portion which joints the mounting portion and the connection wiring portion together. The joint portion extends from an inside to an outside of the case through a gap between the side plate of the case and the liquid crystal panel.