An auxiliary plate (10) is fixed to a rear plane of a housing for fixedly holding a lamp unit (6) having a plurality of lamps. In the auxiliary plate (10), a convex portion and a concave portion are combined. The convex portion has a space between the housing and itself, which is formed by protruding a sheet metal, and the concave portion contacts with the housing by denting the sheet metal. In the auxiliary plate 10, an area for mounting a board vulnerable to heat is formed with the convex portion and an air layer performs as heat insulation. The convex and concave portions are arrayed in a direction where heated air easily flows in another area. Thus, rigidity can be remarkably increased compared to a flat-shaped sheet metal, and heat generated by a backlight is effectively dissipated, as well as a temperature rise and an occurrence of a temperature gradient are suppressed.