A radar apparatus using a pulse compression technique in which a pulse compression process is applied to a receive signal to obtain a compressed pulse signal, the radar apparatus comprising: an antenna adapted to transmit a modulated pulse S2 and to receive an echo from an echo source as well as an automatic response signal from an automatic transponder when the automatic transponder receives a radar transmit signal, the automatic transponder having a dead time after said response; the antenna, while rotating, being further adapted to repeat with a period equal to a second time interval T2 a transmit/receive cycle, in which i) a non-modulated pulse S1 or a trigger pulse is transmitted, ii) at least one modulated pulse S2 is transmitted a first time interval T1 after the transmission of the non-modulated pulse S1 or the trigger pulse, and iii) an echo and/or an automatic response signal occurring after the pulse transmission is received; a receiver for receiving a receive signal for each transmit/receive cycle; a signal separator for separating, from the receive signal, for each transmit/receive cycle, a first separated receive signal having a frequency band corresponding to that of the modulated pulse; an interference eliminator for applying an interference elimination process to the first separated receive signal, in which respective first separated receive signals for two consecutive transmit/receive cycles are compared and any signal component having discontinuity between two consecutive transmit/receive cycles is eliminated from the first separated receive signal; a pulse compressor for applying a pulse compression process to the first separated receive signal having undergone the interference elimination process; and the length of the first time interval T1 being so selected as to be different between two consecutive transmit/receive cycles and to be shorter than the dead time of the automatic transponder. an antenna adapted to transmit a modulated pulse S2 and to receive an echo from an echo source as well as an automatic response signal from an automatic transponder when the automatic transponder receives a radar transmit signal, the automatic transponder having a dead time after said response; the antenna, while rotating, being further adapted to repeat with a period equal to a second time interval T2 a transmit/receive cycle, in which i) a non-modulated pulse S1 or a trigger pulse is transmitted, ii) at least one modulated pulse S2 is transmitted a first time interval T1 after the transmission of the non-modulated pulse S1 or the trigger pulse, and iii) an echo and/or an automatic response signal occurring after the pulse transmission is received; a receiver for receiving a receive signal for each transmit/receive cycle; a signal separator for separating, from the receive signal, for each transmit/receive cycle, a first separated receive signal having a frequency band corresponding to that of the modulated pulse; an interference eliminator for applying an interference elimination process to the first separated receive signal, in which respective first separated receive signals for two consecutive transmit/receive cycles are compared and any signal component having discontinuity between two consecutive transmit/receive cycles is eliminated from the first separated receive signal; a pulse compressor for applying a pulse compression process to the first separated receive signal having undergone the interference elimination process; and the length of the first time interval T1 being so selected as to be different between two consecutive transmit/receive cycles and to be shorter than the dead time of the automatic transponder.