A high-frequency switch comprises: a substrate; a main line electrode provided between two terminals; a stub line electrode with one end thereof connected to the side edge of the main line electrode and the other end thereof grounded; and a ground electrode provided adjacent to the stub line electrode in the width direction thereof; wherein the substrate has a semiconductor activation layer which extends to below the stub line electrode and the ground electrode between at least one side edge of the stub line electrode and the ground electrode; and wherein a gate electrode which extends in the longitudinal direction of the stub line electrode is provided on the semiconductor activation layer between the stub line electrode and the ground electrode, thereby forming an FET structure, thus providing a high-frequency switch and electronic device therewith, capable of using high frequencies, having reduced insertion loss, and high signal cut-off capabilities.