A method for forming an oxide semiconductor film using a sputtering apparatus including a target containing a crystalline In—Ga—Zn oxide, a substrate, and a magnet includes the following steps: generating plasma between the target and the substrate; and separating a flat-plate-like In—Ga—Zn oxide in which a first layer including a gallium atom, a zinc atom, and an oxygen atom, a second layer including an indium atom and an oxygen atom, and a third layer including a gallium atom, a zinc atom, and an oxygen atom are stacked in this order. The flat-plate-like In—Ga—Zn oxide passes through the plasma and thus is negatively charged. Then, while keeping crystallinity, the oxide gets close to a top surface of the substrate, moves over the top surface of the substrate due to a magnetic field of the magnet and current flowing from the substrate to the target, and then is deposited.