A method of manufacturing a sound absorbing board using a honeycomb in which the sound absorbing board is formed by laminating glass fiber mats on both surfaces of the honeycomb and foam-molding polyurethane sheets on surfaces, which are exposed to the outside, of the glass fiber mats, the method comprising: a first step of setting a frequency band for sound absorption performance; a second step of setting a cell size and a thickness of the honeycomb; a third step of setting a range of a thickness (t) of the polyurethane sheets, a range of a diameter (d) of perforations to be formed in the polyurethane sheets, and a porosity of the perforations; a fourth step of obtaining a plurality of sound absorption coefficients according to a frequency change by calculating a respective inherent acoustic impedance of the perforations using the following Equation 1: ζ = R + jX / σ R = 7.337 × 10 − 3 1 + 72.23 M X = 2.2245 × 10 − 5 f 1 + 51 t 1 + 204 d Where ζ denotes the inherent acoustic impedance, R denotes a real part of the impedance, X denotes an imaginary part of the impedance, M denotes a Mach number, σ denotes the porosity of the perforations, t denotes a thickness of the polyurethane sheets and thus of the perforations, and d denotes the diameter of the perforations, while, in order to obtain said plurality of sound absorption coefficients, at least one of the following variables: the thickness (t) of the polyurethane sheets and the diameter (d) of the perforations, is input differently in the respective range set in the third step; and a fifth step of marking positions of the perforations on at least one of the polyurethane sheets with at least one diameter (d) of the perforations at which the sound absorption coefficient is high in the frequency band set in the first step among sound absorption coefficients obtained in the fourth step. a first step of setting a frequency band for sound absorption performance; a second step of setting a cell size and a thickness of the honeycomb; a third step of setting a range of a thickness (t) of the polyurethane sheets, a range of a diameter (d) of perforations to be formed in the polyurethane sheets, and a porosity of the perforations; a fourth step of obtaining a plurality of sound absorption coefficients according to a frequency change by calculating a respective inherent acoustic impedance of the perforations using the following Equation 1: ζ = R + jX / σ R = 7.337 × 10 − 3 1 + 72.23 M X = 2.2245 × 10 − 5 f 1 + 51 t 1 + 204 d Where ζ denotes the inherent acoustic impedance, R denotes a real part of the impedance, X denotes an imaginary part of the impedance, M denotes a Mach number, σ denotes the porosity of the perforations, t denotes a thickness of the polyurethane sheets and thus of the perforations, and d denotes the diameter of the perforations, while, in order to obtain said plurality of sound absorption coefficients, at least one of the following variables: the thickness (t) of the polyurethane sheets and the diameter (d) of the perforations, is input differently in the respective range set in the third step; and a fifth step of marking positions of the perforations on at least one of the polyurethane sheets with at least one diameter (d) of the perforations at which the sound absorption coefficient is high in the frequency band set in the first step among sound absorption coefficients obtained in the fourth step.