A multi-feed horn includes a first feed horn, a second feed horn and a third feed horn which are connected to a first waveguide, a second waveguide and a third waveguide, respectively. The first feed horn is provided with a first proximal end opening and a first tip opening which are rectangular in shape, the second feed horn is provided with a second proximal end opening and a second tip opening which are rectangular in shape, and the third feed horn is provided with a third proximal end opening and a third tip opening which are rectangular in shape. Consequently, a multi-feed horn, a low noise block downconverter and an antenna apparatus which allow a further improvement in the reception characteristic and in the manufacturing accuracy can be provided.