In order to lessen the deterioration of the VSWR, a plural-reflector antenna system is provided wherein an appropriately shaped vertex matching plate is disposed on the subreflector and electric waves that reenter the primary radiator are cancelled out. The electric waves radiated from the primary radiator are reflected by the subreflector and are radiated into space after being reflected by the main reflector. The passing area in the horn aperture, through which the reflected waves from the vertex matching plate pass, is made to be analogous to the aperture of the primary radiator, by defining the vertex matching plate as an ellipsoid, and by orienting its minor-axis direction in the major-axis direction of the main reflector and its major-axis direction, in the minor-axis direction of the main reflector.