Roughly speaking, Stein's method is a method to evaluate the distance between probability distributions by means of differential operators, while Malliavin calculus is a theory to treat the derivatives of the functionals on the Wiener space and the functionals of general Gaussian processes. In this talk, I will give a basic description of Malliavin-Stein's method, which is a combination of Stein's method and Malliavin calculus, and introduce related problems if time permits.