A quantum interference device comprises a semi-insulating GaAs substrate; GaAs and AlGaAs layers sequentially formed with high purity on the substrate; a two-dimensional electron gas layer formed in the GaAs layer and serving as a channel; source/drain regions formed on the semi-insulating GaAs substrate and at both ends of a laminated portion composed of the GaAs/AlGaAs layers; and a gate formed on the AlGaAs layer and having a periodic structure wherein the length thereof varies in a periodic manner in a transverse direction. In the device, the electron gas layer formed in the GaAs layer is used as an electron path, and the phases of electrons passing along different electron paths are caused to interfere with each other by the gate, thereby causing the current of a drain therein to be maximized or minimized. The transconductance can be significantly increased.