[en] An attempt has been made to use the Monte Carlo method for a shell-model calculation of the strength function. It is found that the method works quite well to calculate the Gamow-Teller strength function in ₂₀₈Bi. The widths evaluated from the strength functions are in excellent agreement with those by the Golden Rule in the truncated model space. The spreading width of the Gamow-Teller giant resonance is estimated to be rather than that deduced from the reaction ₂₀₈Pb(p, n)₂₀₈Bi. Interference between particle and hole spreadings reduces the resonance width appreciably. (orig.)