A radar can detect target azimuths located outside and adjacent to a scanning angular range of a beam by determining changes in received signal strength (a signal-strength profile) in the azimuthal direction as a function of a beam azimuth in a predetermined scanning angular range, and estimating the target azimuth causing the signal-strength profile from the signal-strength profile, which is portion of a convex located adjacent to the outermost angle in the scanning angular range. For example, the target azimuth is estimated by a ratio between the received signal strength at the outermost angle of about 10.0.degree. and the received signal strength at about 9.5.degree., which is one beam inside the outermost position.