A display device comprising: a substrate including a display area and a non-display area, the display area being configured to display images and located medially, the non-display area being located closer to peripheral edges of the substrate so as to surround the display area; a display area transistor disposed in the display area; a non-display area transistor disposed in the non-display area; a gate electrode included in the non-display area transistor; an oxide semiconductor film included in the non-display area transistor, at least a portion of the oxide semiconductor film overlapping the gate electrode in a plan view; a source electrode included in the non-display area transistor, at least a portion of the source electrode being layered on the oxide semiconductor film in a plan view and connected to the oxide semiconductor film; a drain electrode included in the non-display area transistor, at least a portion of the drain electrode being layered on the oxide semiconductor film and connected to the oxide semiconductor film with a gap between the source electrode and the drain electrode; a protection film made of silicon oxide for protecting the oxide semiconductor film, the protection film being disposed between the source electrode and the oxide semiconductor film and between the drain electrode and the oxide semiconductor film, the protection film including a pair of holes (29e1, 29e2) formed at positions overlapping the source electrode and the drain electrode, respectively, in a plan view and through which the source electrode and the drain electrode are connected to the oxide semiconductor film; and an insulator covering the source electrode, the drain electrode, and the oxide semiconductor film from above, the insulator having a multilayer structure including a lower insulator and an upper insulator, characterized in that the lower insulator, which is made of silicon oxide, is disposed in a lower layer so that hydrogen desorbed from the upper insulator is less likely to permeate through the lower insulator, the upper insulator, which is made of silicon nitride, is disposed in an upper layer so that moisture is less likely to permeate through the upper insulator and less likely to reach the oxide semiconductor film, and the upper insulator has a thickness in a range from 35 nm to 75 nm. a substrate including a display area and a non-display area, the display area being configured to display images and located medially, the non-display area being located closer to peripheral edges of the substrate so as to surround the display area; a display area transistor disposed in the display area; a non-display area transistor disposed in the non-display area; a gate electrode included in the non-display area transistor; an oxide semiconductor film included in the non-display area transistor, at least a portion of the oxide semiconductor film overlapping the gate electrode in a plan view; a source electrode included in the non-display area transistor, at least a portion of the source electrode being layered on the oxide semiconductor film in a plan view and connected to the oxide semiconductor film; a drain electrode included in the non-display area transistor, at least a portion of the drain electrode being layered on the oxide semiconductor film and connected to the oxide semiconductor film with a gap between the source electrode and the drain electrode; a protection film made of silicon oxide for protecting the oxide semiconductor film, the protection film being disposed between the source electrode and the oxide semiconductor film and between the drain electrode and the oxide semiconductor film, the protection film including a pair of holes (29e1, 29e2) formed at positions overlapping the source electrode and the drain electrode, respectively, in a plan view and through which the source electrode and the drain electrode are connected to the oxide semiconductor film; and an insulator covering the source electrode, the drain electrode, and the oxide semiconductor film from above, the insulator having a multilayer structure including a lower insulator and an upper insulator, characterized in that the lower insulator, which is made of silicon oxide, is disposed in a lower layer so that hydrogen desorbed from the upper insulator is less likely to permeate through the lower insulator, the upper insulator, which is made of silicon nitride, is disposed in an upper layer so that moisture is less likely to permeate through the upper insulator and less likely to reach the oxide semiconductor film, and the upper insulator has a thickness in a range from 35 nm to 75 nm.