To improve the display quality of a display device, the display device includes a display section and a frame section surrounding a periphery of the display section. A substrate in the display device includes a conductor pattern constituting a circuit section and an insulating film serving as an organic film covering the conductor pattern. The insulating film extends to a peripheral edge of the substrate. A slit, which penetrates the insulating film in a thickness direction, is formed in a corner part of the insulating film. The slit is formed at a position not overlapping the circuit section.