A manufacturing method of an oxide semiconductor thin film transistor according to the disclosure includes the following. A source and a drain are formed. A channel layer is formed between the source and the drain, wherein the channel layer is separated from the source and the drain. An insulation layer is formed, wherein the insulation layer covers the source, the drain, and the channel layer. A first conductor is at least formed in a first opening of the insulation layer, wherein the first conductor contacts the source and the channel layer. A second conductor is at least formed in a second opening of the insulation layer, wherein the second conductor contacts the drain and the channel layer.