  We propose a new computational method for astrophysical reaction rate of
radiative capture process. In the method, an evolution of a wave function is
calculated along the imaginary-time axis which is identified as the inverse
temperature. It enables direct evaluation of reaction rate as a function of
temperature without solving any scattering problem. The method is tested for
two-body radiative capture reaction, ${^{16}{\rm O}}(\alpha,\gamma){^{20}{\rm
Ne}}$, showing that it gives identical results to that calculated by the
ordinary procedure. The new method will be suited for calculation of
triple-alpha radiative capture rate for which an explicit construction of the
scattering solution is difficult.
