An angular error detecting device detects an angular error in a receiving direction of a frequency signal from a tracking target with respect to a front direction of an antenna based on a phase difference of a first reception signal received at a first receiving unit of the antenna and a second reception signal received at a second receiving unit having a receiving position in the antenna different from a receiving position of the first receiving unit. The angular error detecting device includes a reception signal output unit, a pilot signal supply unit, a pilot phase difference detection unit, a correction unit, and an angular error detection unit. The angular error detection unit detects the angular error based on the one side corrected at the correction unit and the other side that is not corrected of the sum signal and the difference signal.