An acoustic signal processing apparatus (111; 311) comprising: a first transaural processing unit (121; 321) that generates a first binaural signal for a first input signal, which is an acoustic signal for a first virtual sound source deviated to left or right from a median plane of a predetermined listening position, by using a first head-related transfer function between an ear of a listener at the listening position farther from the first virtual sound source and the first virtual sound source, generates a second binaural signal for the first input signal by using a second head-related transfer function between an ear of the listener closer to the first virtual sound source and the first virtual sound source, and generates a first acoustic signal and a second acoustic signal by performing crosstalk correction processing on the first binaural signal and the second binaural signal as well as attenuates a component of a first frequency band and a component of a second frequency band in the first input signal or the second binaural signal to attenuate the component of the first frequency band and the component of the second frequency band of the first acoustic signal and the second acoustic signal, the first frequency band being lowest and the second frequency band being second lowest at a predetermined first frequency or more of frequency bands in which notches, which are negative peaks with amplitude of a predetermined depth or deeper, appear in the first head-related transfer function; and a first auxiliary signal synthesizing unit that generates a third acoustic signal by adding a first auxiliary signal to the first acoustic signal, the first auxiliary signal including a component of a predetermined third frequency band of the first input signal, in which the component of the first frequency band and the component of the second frequency band are attenuated, or the component of the third frequency band of the second binaural signal, in which the component of the first frequency band and the component of the second frequency band are attenuated. a first transaural processing unit (121; 321) that generates a first binaural signal for a first input signal, which is an acoustic signal for a first virtual sound source deviated to left or right from a median plane of a predetermined listening position, by using a first head-related transfer function between an ear of a listener at the listening position farther from the first virtual sound source and the first virtual sound source, generates a second binaural signal for the first input signal by using a second head-related transfer function between an ear of the listener closer to the first virtual sound source and the first virtual sound source, and generates a first acoustic signal and a second acoustic signal by performing crosstalk correction processing on the first binaural signal and the second binaural signal as well as attenuates a component of a first frequency band and a component of a second frequency band in the first input signal or the second binaural signal to attenuate the component of the first frequency band and the component of the second frequency band of the first acoustic signal and the second acoustic signal, the first frequency band being lowest and the second frequency band being second lowest at a predetermined first frequency or more of frequency bands in which notches, which are negative peaks with amplitude of a predetermined depth or deeper, appear in the first head-related transfer function; and a first auxiliary signal synthesizing unit that generates a third acoustic signal by adding a first auxiliary signal to the first acoustic signal, the first auxiliary signal including a component of a predetermined third frequency band of the first input signal, in which the component of the first frequency band and the component of the second frequency band are attenuated, or the component of the third frequency band of the second binaural signal, in which the component of the first frequency band and the component of the second frequency band are attenuated.