The present invention provides a direction finder antenna that includes an antenna mount having one flat portion and four extensible whip antenna elements respectively upright provided rotatably at antenna upright-provided points formed on one circumference at an antenna upright-provided surface. The four extensible whip antenna elements can be rotatably set to arbitrary angular positions lying in sector-shaped areas each having an open angle of 180° orthogonal to the one circumference, which are formed on the antenna upright-provided surface side, centering on the respective antenna upright-provided points at the antenna upright-provided surface.