To provide an oxide semiconductor with a novel structure. Such an oxide semiconductor is composed of an aggregation of a plurality of InGaZnO4 crystals each of which is larger than or equal to 1 nm and smaller than or equal to 3 nm, and in the oxide semiconductor, the plurality of InGaZnO4 crystals have no orientation. Alternatively, such an oxide semiconductor is such that a diffraction pattern like a halo pattern is observed by electron diffraction measurement performed by using an electron beam with a probe diameter larger than or equal to 300 nm, and that a diffraction pattern having a plurality of spots arranged circularly is observed by electron diffraction measurement performed by using an electron beam with a probe diameter larger than or equal to 1 nm and smaller than or equal to 30 nm.