  We have been developing a program package called GRACE/SUSY-loop which
automatically calculates the MSSM amplitudes in one-loop order. We present
numerical results of calculations for pair-production and three-body decay of
the lighter stop ($\widetilde{t}_1$) at the International Linear Collider (ILC)
using GRACE/SUSY-loop. Since the distributions of missing transverse energy
(MET) depend on mass spectrum of SUSY particles, we consider two scenarios on
three-body decay of $\widetilde{t}_1$. In these scenarios, both QCD and EW
corrections have positive sign for decay widths and cross sections.
