A target detection device comprising: a detection unit detecting amplitude or power of a received signal of an electromagnetic wave reflected by a target; a plurality of target detection units (14-n) respectively performing detection processing of targets which are different in spatial extent from each other on a basis of a detection result of the amplitude or power by the detection unit; and at least one determination processing unit (16-m) determining presence or absence of a target from a result of the detection processing of targets obtained by the plurality of target detection units, wherein each of the plurality of target detection units performs constant false alarm rate processing as the detection processing of a target, the target detection device charaterized in that the constant false alarm rate processing is performed in which ranges of guard cells are different from each other among the plurality of target detection units, weight values each corresponding to a spatial extent of a detectable target are set for the plurality of target detection units, respectively, and the at least one determination processing unit determines presence or absence of a target by calculating, for the plurality of target detection units, multiplication values of the weight values set for the plurality of target detection units and detection values each indicating the result of the detection processing of a target by each of the plurality of target detection units, respectively, and by comparing a sum of the multiplication values of the weight values and the detection values of the plurality of target detection units and a target determination threshold. a detection unit detecting amplitude or power of a received signal of an electromagnetic wave reflected by a target; a plurality of target detection units (14-n) respectively performing detection processing of targets which are different in spatial extent from each other on a basis of a detection result of the amplitude or power by the detection unit; and at least one determination processing unit (16-m) determining presence or absence of a target from a result of the detection processing of targets obtained by the plurality of target detection units, wherein each of the plurality of target detection units performs constant false alarm rate processing as the detection processing of a target, the target detection device charaterized in that the constant false alarm rate processing is performed in which ranges of guard cells are different from each other among the plurality of target detection units, weight values each corresponding to a spatial extent of a detectable target are set for the plurality of target detection units, respectively, and the at least one determination processing unit determines presence or absence of a target by calculating, for the plurality of target detection units, multiplication values of the weight values set for the plurality of target detection units and detection values each indicating the result of the detection processing of a target by each of the plurality of target detection units, respectively, and by comparing a sum of the multiplication values of the weight values and the detection values of the plurality of target detection units and a target determination threshold.