PURPOSE: To obtain a feedback type microwave amplifier in which feedback length can be remarkably reduced and with superior characteristic by forming a feedback circuit so as to pass over or under a plane where an amplifier element is located.

CONSTITUTION: A field effect transistor FET 13 is formed so as to be floated over a dielectric substrate plane, and the feedback circuit 34 is comprised on a floated dielectric substrate plane. By such configuration, the gate terminal G of the FET 13 can be connected to the drain terminal D in a minimum distance, and also, the electric length of the feedback circuit 34 can be reduced. Also, two-layer structure in which the amplifier element is arranged on the substrate plane, and the intermediate part of the feedback circuit 34 is passed over the upper side of the amplifier element by floating can be adopted. When the amplifier element is grounded at two points, the electric length of the feedback circuit 34 can be reduced compared with a device in which the feedback circuit 34 bypasses a source terminal, etc., by passing the feedback circuit 34 through an inside area held in between the two points even when the amplifier element and a plane where the feedback circuit 34 is comprised are formed on the same plane.