[Problem] To provide a waveguide tube connection device that readily improves operability. [Solution] The device comprises two waveguide tube connection clamps 1 each having a pair of clamp pieces 11 disposed to face each other so as to interpose the outer peripheral edges of flanges 20 disposed to face each other, and a tightening means 12 for pressing the clamp pieces 11 against the outer peripheral edges of the flanges 20. The clamp piece 1 comprises: two contact members 111 having first surfaces which are brought into contact with the surfaces of the flanges 20, which are disposed to face each other, the surfaces being on the side opposite to the mutually facing surfaces of the flanges 20, second surfaces which are brought into contact with the side surfaces of the waveguide tubes, and third surfaces which are tapered surfaces on the side opposite to the mutually facing surfaces of the flanges 20; and a pressing member 112 of a substantially V-shaped cross section which has two inclined surfaces that are
