Abstract: A field effect transistor includes a layer structure made of compound semiconductor (111) provided on a semiconductor substrate (110) made of GaAs or InP, as an operation layer, and employs a first field plate electrode (116) and a second field plate electrode (118). The second field plate electrode includes a shielding part (119) located in the region between the first field plate electrode and a drain electrode (114), and serves to shield the first field plate electrode from the drain electrode. When, in the cross sectional view in the gate length direction, the length in the gate length direction of an overlap region, in which the second field plate electrode overlaps the upper part of a structure composed of the first field plate electrode and a gate electrode (113), is designated as Lol, and the gate length is Lg, the relation expressed as 0?Lol/Lg?1 holds.