The objective of this study is to examine numerically the laminar separated flow in a symmetric sudden expansion channel. As a computational model of the symmetric sudden expansion channel, the two-dimensional channel with backward facing steps on both upper and lower walls were considered, and a small suction hole was placed at the lower wall underneath the step. Two-dimensional time-dependent Navier-Stokes equations and the equation of continuity were solved numerically by the finite different method. The calculation was performed on the conditions of suction flow rate dQ=0.0 and dQ=0.02 for the only case of Reynolds number Re=160 and expansion ratio (H+2h) /H=2.0 (H being channel width in the upstream of step and h being the step height). In this report, from the calculation results, the behaviors of flow pattern, the contours and vector distribution of pressure gradient with passage of time were presented. In addition, the convergence process in the steady state of flow was shown and was discussed for the convergence criterion in a steady state was satisfied.