An object to be achieved by an embodiment of the present invention is to provide a radar apparatus, a signal processing apparatus, and a method that reduce interference caused to a reception signal by a transmission signal during transmission of a signal. To achieve the above object, a radar apparatus of an embodiment includes: a transmitter configured to transmit a pulse signal; a receiver configured to receive a reception signal including a first signal as the pulse signal reflected by an observation target and an interference signal provided in accordance with the pulse signal; and a processor configured to generate a separated signal in which the reception signal is, on a time axis, separated into a first component corresponding to the first signal and an interference component corresponding to the interference signal by using a first reference signal generated based on the pulse signal and reduce the interference component.