A semiconductor device includes a switching unit that is provided on a substrate and controls selection of a high-frequency signal, a low-frequency circuit that is provided on the substrate and processes signals having a frequency lower than that of the switching unit, a first ground portion connected to a ground node of the low-frequency circuit, a ground conductor provided on the substrate, connected to the first ground portion at a first connection position, and connected to the ground node of the switching unit at a second connection position, and a second ground portion connected to the ground conductor, the second ground portion being closer to the second connection position than the first connection position.