Provided is a filter coefficient optimization technology that makes it possible to design a stable beamformer having a good quality by considering the relationship of a filter coefficient between adjacent frequency bins. A filter coefficient optimization apparatus includes an optimization unit that calculates an optimum value of a filter coefficient w={w1, . . . , wF} (wf is a filter coefficient of a frequency bin f) of a beamformer that emphasizes sound (target sound) from D sound source, af,d being an array manifold vector in the frequency bin f corresponding to a sound wave that comes from an angular direction θd in which a sound source d exists, the sound wave being a plane wave, the optimization unit calculating the optimum value based on an optimization problem of a cost function defined using a sum of a sum of a cost function LMV_f(wf) and a predetermined regularization term, under a predetermined constraint condition, the predetermined regularization term being defined using a difference in phase between adjacent frequency bins relevant to a response wfHaf,d of the beamformer in the frequency bin f for the angular direction θd.