An object detection device comprising: an active sensor configured to transmit a detection wave to a predetermined detection area, and to receive the detection wave reflected by a detection target object for detecting the presence or absence of the detection target object in the predetermined detection area, and to output a sensor signal; a signal processor configured to divide the sensor signal output from said active sensor into divided sensor signals, and to output the divided sensor signals, wherein the divided sensor signals correspond to a plurality of frequency bands; a frequency analyzer configured to detect a signal intensity of individual frequencies of the sensor signal output from said active sensor spaced apart from each other in 1 [Hz] units; characterized by a determining unit configured determine the presence or absence of the detection target object by comparing non-invalidated divided sensor signals output from said signal processor with a plurality of predetermined threshold values respectively, wherein said plurality of predetermined threshold values are defined with respect to the plurality of frequency bands, respectively; and a noise rejection unit configured to cause said determining unit to invalidate, from among said divided sensor signals, a divided sensor signal of a frequency band including a noise of a particular one of said individual frequencies, wherein noise is detected when the signal intensity of the particular individual frequency output from the frequency analyzer is greater than or equal to a defined value, when the noise is detected constantly from the signal intensity of said particular individual frequency output from said frequency analyzer. an active sensor configured to transmit a detection wave to a predetermined detection area, and to receive the detection wave reflected by a detection target object for detecting the presence or absence of the detection target object in the predetermined detection area, and to output a sensor signal; a signal processor configured to divide the sensor signal output from said active sensor into divided sensor signals, and to output the divided sensor signals, wherein the divided sensor signals correspond to a plurality of frequency bands; a frequency analyzer configured to detect a signal intensity of individual frequencies of the sensor signal output from said active sensor spaced apart from each other in 1 [Hz] units; characterized by a determining unit configured determine the presence or absence of the detection target object by comparing non-invalidated divided sensor signals output from said signal processor with a plurality of predetermined threshold values respectively, wherein said plurality of predetermined threshold values are defined with respect to the plurality of frequency bands, respectively; and a noise rejection unit configured to cause said determining unit to invalidate, from among said divided sensor signals, a divided sensor signal of a frequency band including a noise of a particular one of said individual frequencies, wherein noise is detected when the signal intensity of the particular individual frequency output from the frequency analyzer is greater than or equal to a defined value, when the noise is detected constantly from the signal intensity of said particular individual frequency output from said frequency analyzer.