In a radio wave lens antenna, a lens cover for covering the surface of the lens is stably fixed to the reflector. The antenna has a semispherical Luneberg lens, a semispherical shell-shaped lens cover for covering the surface of the lens, a radio wave reflector, a ring-shaped plate placed along the outer circumference of the lens, a primary feed placed at the focal point of the lens, and a holding part for the primary feed. A flange provided at the opening edge of the lens cover is clamped by the reflector and the plate to fix the lens cover to the reflector, and more preferably, the lens cover is caused to be in contact with the lens, and the lens is pressed also in the radial direction by the plate via the lens cover.