A DS-SS radar 10 detects an object in such a way that a code generator 21, an oscillator 32, and an antenna 24 repeatedly send a sending signal modulated with a predetermined-frequency code generated by the code generator 21, an A/D converter 45 samples the code, included in the reflected wave of the sending signal reflected by an object, with a sampling period lower than the period of the code, and a correlator 46 calculates the correlation between the reference code, generated by re-arranging the code from the code generator 21 at an interval of Nsp, and the sampling data converted by the A/D converter 45.