To provide an antenna characteristic measuring device capable of realizing accurate measurement.

This antenna characteristic measuring device measures the directional pattern of an antenna. The device has a transmission antenna connected to a signal generator and a rotary stage rotatably supporting a receiving antenna as a measurement object. The rotary stage includes a disk-like earth plate 134. The rotary state has a support plate, which is a disk for supporting the earth plate 134 and has a support plate 133 made of foam resin. The earth plate 134 is made of metal and has a thickness of 0.3 mm or less.