A target detection device includes: a sound source which projects a sound pulse; a transducer array disposed in a region for receiving a forward scattered wave from an object in the propagation environment; an addition processing unit which extracts only a signal of the forward scattered wave by applying vector addition processing on a reference signal in a reference sound field received when an obstacle exists in the propagation environment and a mixed signal in a mixed sound field received when the target exists with the obstacle; a phase conjugation determination unit which checks whether a phase conjugacy is established by receiving the signal of the extracted forward scattered wave and employing a passive phase conjugation for determining the reference sound field; and a time reversal processing unit which generates a time reversal signal on condition that the phase conjugation determination unit judges that the phase conjugacy is established.