To attain miniaturization and improvement in radiation characteristics concerning the antenna system of a mechanical scan type composed of the assembly of a lens and a rotary reflector.

This antenna system is provided with a primary radiator 2 for radiating radio wave beams, convergent reflector 3 for changing the direction of these radiated radio wave beams while decreasing the spread of these beams by reflecting the beams while converging them, beam scanning mechanisms 5, 6 and 7 for scanning the direction changed radio wave beams by driving this convergent reflector 3 and lens such as a dielectric lens 4 for decreasing the spread of radio wave beams reflected by the convergent reflector 3 by converging these beams.