A signal processing unit in a radar device calculates a change amount Y (=log(P)−log(Pb)) between a power P of a current arrival echo and a power of a previous arrival echo arrived before an observation period TSW. A memory unit in the radar device stores, every type of objects, a probability distribution of the change amount Y calculated from the arrival echo from the object. On the basis of the calculated change amount Y and the probability distribution, the signal processing unit determines a probability Pr to obtain the change amount Y every type of object, and determines that the object having the maximum probability Pr is the object which transmits the current arrival echo.