A tunable microwave bandstop filter device comprises a main microwave transmission line (1), at least one filter cell comprising a coupled line segment (4) coupled to the main transmission line (1) and arranged parallel to and remotely from the latter, and also a tunable LC resonant circuit (5, 6). According to the invention, the tunable LC resonant circuit (5, 6) is placed between one of the ends of the line segment (4) and the main microwave transmission line (1).