The main purpose of this paper is to consider the robust stability analysis of time-delay systems based on the parameter plane method. The simple and systematic procedure proposed for solving this problem easily obtains the exact stability boundaries of time-delay systems. First, the relation between state-space representation and s-domain characteristic equations is analyzed. The effects of both the state matrix and time-delay on stability are addressed by this approach. System stabilization by state feedback gain is also derived. Performance tests of the proposed procedure confirm that it obtains more information compared with procedures reported in the literature.