The effects of the location of the baffle on mixing pattern in laminar mixing is shown in this study. Decolorization experiments were conducted based on an oxidation-reduction reaction to investigate the mixing pattern. As a result, isolated mixing regions (IMR) like doughnut-rings were eliminated by setting the baffle at the optimum location, where the baffle and the IMR crossed each other. The velocity profile was measured by using particle image velocimetry under the baffle condition. The IMR was dissipated due to making unstable circulation flow when the baffle was placed with clearance between the baffle and the wall. It was shown that using conventional mixing equipment can eliminate the IMR easily by placing the baffle with clearance.