A microphone array signal processing apparatus which is capable of picking up sound in a low frequency band even with a compact microphone array. The microphone array signal processing apparatus is comprised of delay devices (411-1 to 411-M) that add delays to the respective ones of a plurality of sound signals output from the respective ones of a plurality of microphones constituting the microphone array, an adder (412) that sums the plurality of sound signals with the respective delays added thereto, a harmonic structure detecting section (421) that detects a harmonic structure of sound included in the sound signal, and a filtering processing section (422) that selectively passes predetermined frequency components based upon the detected harmonic structure.