A backlight unit, comprising: a base substrate in which a light emitting area and a non-light emitting area are defined; a wiring layer comprising: a lower conductive layer disposed on the base substrate; an intermediate conductive layer disposed on the lower conductive layer; and an upper conductive layer disposed on the intermediate conductive layer; a coupling force between the lower conductive layer and the base substrate is greater than a coupling force between the intermediate conductive layer and the base substrate; the upper conductive layer is made of a conductive material having better corrosion resistance than the intermediate conductive layer; the intermediate conductive layer includes copper or a copper alloy; a light emitting element disposed on the wiring layer in the light emitting area; a connection member (SR1, SR2) electrically connecting the light emitting element and the wiring layer, the connection member (SR1, SR2) contacting the intermediate conductive layer of the wiring layer and the light emitting element; a backlight flexible substrate electrically connected to the wiring layer in the non-light emitting area; and a pad connection member electrically connecting the wiring layer and the backlight flexible substrate in the non-light emitting area, the pad connection member contacting the upper conductive layer of the wiring layer, wherein a coupling force between the connection member (SR1, SR2) and the intermediate conductive layer of the wiring layer is greater than a coupling force between the connection member (SR1, SR2) and the upper conductive layer. a base substrate in which a light emitting area and a non-light emitting area are defined; a wiring layer comprising: a lower conductive layer disposed on the base substrate; an intermediate conductive layer disposed on the lower conductive layer; and an upper conductive layer disposed on the intermediate conductive layer; a coupling force between the lower conductive layer and the base substrate is greater than a coupling force between the intermediate conductive layer and the base substrate; the upper conductive layer is made of a conductive material having better corrosion resistance than the intermediate conductive layer; the intermediate conductive layer includes copper or a copper alloy; a lower conductive layer disposed on the base substrate; an intermediate conductive layer disposed on the lower conductive layer; and an upper conductive layer disposed on the intermediate conductive layer; a coupling force between the lower conductive layer and the base substrate is greater than a coupling force between the intermediate conductive layer and the base substrate; the upper conductive layer is made of a conductive material having better corrosion resistance than the intermediate conductive layer; the intermediate conductive layer includes copper or a copper alloy; a light emitting element disposed on the wiring layer in the light emitting area; a connection member (SR1, SR2) electrically connecting the light emitting element and the wiring layer, the connection member (SR1, SR2) contacting the intermediate conductive layer of the wiring layer and the light emitting element; a backlight flexible substrate electrically connected to the wiring layer in the non-light emitting area; and a pad connection member electrically connecting the wiring layer and the backlight flexible substrate in the non-light emitting area, the pad connection member contacting the upper conductive layer of the wiring layer, wherein a coupling force between the connection member (SR1, SR2) and the intermediate conductive layer of the wiring layer is greater than a coupling force between the connection member (SR1, SR2) and the upper conductive layer.