A decorative member composing a casing includes: a resin layer (2) having a front surface (2b) and a back surface (2a); and a reflective layer (3) formed on the back surface (2a) of the resin layer (2). The back surface (2a) of the resin layer (2) includes a receding surface (21) formed therein. The receding surface recedes gradually toward the front surface (2b) to change a thickness of the resin layer (2). The receding surface (21) is a concave surface forming a depression that opens while broadening. The back surface (2a) of the resin layer (2) has a reference surface (22) around the receding surface (21), and a portion of the reference surface (22) facing an internal space of the casing is a roughened area (4).