An active matrix substrate includes a TFT. The TFT includes a gate electrode, a semiconductor layer overlapping the gate electrode with a gate insulating film interposed therebetween, and a source electrode and a drain electrode disposed on the semiconductor layer. The source electrode, the drain electrode, and the semiconductor layer are covered with a first insulating film. The gate insulating film includes a first stepped portion in a portion covering a peripheral portion of the gate electrode. The first insulating film includes a first opening at a position overlapping a portion of the first stepped portion that is not covered with the source electrode and the drain electrode in a plan view.