Abstract: A field effect transistor includes: a semiconductor region including a first inactive region, an active region, and a second inactive region arranged side by side in a first direction; a gate electrode, a source electrode, and a drain electrode on the active region; a gate pad on the first inactive region; a gate guard on and in contact with the semiconductor region, the gate guard being apart from the gate pad and located between an edge on the first inactive region side of the semiconductor region and the gate pad; a drain pad on the second inactive region; a drain guard on and in contact with the semiconductor region, the drain guard being apart from the drain pad and located between an edge on the second inactive region side of the semiconductor region and the drain pad; and a metal film electrically connected to the gate guard.