A multi-input noise suppression device which performs a process using a main signal and at least one noise reference signal, the main signal including a target sound component and a noise component, the noise reference signal including a noise component, and said multi-input noise suppression device comprising: a power spectrum calculation unit configured to perform a calculation process to obtain a main power spectrum of the main signal and a reference power spectrum of the noise reference signal, after each expiration of a unit clock time corresponding to a unit of sound processing; a power spectrum estimation unit configured to perform, every time the calculation process is performed, an estimation process to obtain an estimated target sound power spectrum (P S (ω)) that is assumed to be a power spectrum of a target sound, based on the main power spectrum and on a first calculated value obtained by at least multiplying the reference power spectrum by a first weight coefficient; and a coefficient update unit configured to update, every time the estimation process is performed, the first weight coefficient and a second weight coefficient so that a second calculated value approximates to the main power spectrum, the second calculated value being obtained by adding at least two values obtained by multiplying the reference power spectrum and the estimated target sound power spectrum by the first weight coefficient and the second weight coefficient, respectively, wherein said power spectrum estimation unit is configured to, in the estimation process, (i) obtain the estimated target power spectrum by at least multiplying the reference power spectrum calculated upon an expiration of a k+1 th unit clock time by the first weight coefficient updated by said coefficient update unit upon an expiration of a k th unit clock time, and (ii) output the obtained estimated target power spectrum, k being an integer equal to or greater than 1. a power spectrum calculation unit configured to perform a calculation process to obtain a main power spectrum of the main signal and a reference power spectrum of the noise reference signal, after each expiration of a unit clock time corresponding to a unit of sound processing; a power spectrum estimation unit configured to perform, every time the calculation process is performed, an estimation process to obtain an estimated target sound power spectrum (P S (ω)) that is assumed to be a power spectrum of a target sound, based on the main power spectrum and on a first calculated value obtained by at least multiplying the reference power spectrum by a first weight coefficient; and a coefficient update unit configured to update, every time the estimation process is performed, the first weight coefficient and a second weight coefficient so that a second calculated value approximates to the main power spectrum, the second calculated value being obtained by adding at least two values obtained by multiplying the reference power spectrum and the estimated target sound power spectrum by the first weight coefficient and the second weight coefficient, respectively, wherein said power spectrum estimation unit is configured to, in the estimation process, (i) obtain the estimated target power spectrum by at least multiplying the reference power spectrum calculated upon an expiration of a k+1 th unit clock time by the first weight coefficient updated by said coefficient update unit upon an expiration of a k th unit clock time, and (ii) output the obtained estimated target power spectrum, k being an integer equal to or greater than 1.