An object detection apparatus 1 includes: an emitting unit 101 for emitting an RF transmission signal; a receiving unit 201 for receiving, if the RF transmission signal is reflected off an object, the reflected RF transmission signal as an RF reception signal; an IF signal generating unit 202 for generating, in every period, a complex IF signal based on a signal obtained by mixing the RF transmission signal with the RF reception signal; a position detecting unit 203 for detecting the position of the object based on an evaluation function generated based on the complex IF signal generated in every period; and a displacement detecting unit 204 for detecting a displacement of the object based on the position of the object and the phase of complex reflectance of the object calculated based on the complex IF signal.