The present invention provides a thin-film transistor substrate including a base substrate and a thin-film transistor, the thin-film transistor including: a gate electrode; a gate insulating layer; a source electrode and a drain electrode; and an oxide semiconductor layer in this order. The source electrode and the drain electrode each include a first conductive layer and a second conductive layer covering the first conductive layer. The second conductive layer contains at least one element selected from the group consisting of molybdenum, tantalum, tungsten, and nickel. The gate insulating layer in a region between the source electrode and the drain electrode has a smaller thickness than in a region below the source electrode and in a region below the drain electrode.