An incoming direction estimation apparatus estimates an incoming direction of a radar wave using three or more sensors or antennas simultaneously. An arithmetic expression for estimating an incoming direction of a radar wave is configured as sin−1((1/2πa)*tan−1b). The “a” is d/λ determined by an antenna interval and by a wavelength λ of a carrier, or such, carrying the radar wave. A simultaneous use of three antennas makes it possible to set the a as a value depending on a value d0=a0λ based on the interval between first antennas and value d1=a1λ based on the interval between second antennas. Therefore, if a wide field of vision of an incoming direction is needed, it is only necessary to adjust (d1−d0)/λ=(a1−a0), in place of the absolute interval of antennas a=d/λ, thereby making it possible to lessen a limitation on the design of antennas and set a field of vision of the incoming direction appropriately.