An acoustic signal processing device includes an acoustic signal processing unit configured to calculate a spectrum of each acoustic signal and a steering vector having m elements on the basis of m acoustic signals converted into m digital signals by sampling m analog signals representing sounds collected by m microphones (m is an integer of 1 or more and M or less, and M is an integer of 2 or more), and to estimate a sampling frequency ωm in the sampling on the basis of the spectrum, the steering vector, and a sampling frequency ωideal that is a predetermined value.