In the purpose of development of new elongational rheometer to estimate planar elongational viscosity for various fluids, we investigated the way to generate planar elongational flow by using two-dimensional opposing flow. The relationship between elongation rate at the stagnation point and flow rate was measured from results of flow visualization. And elongational stress was evaluated from flow birefringence at the stagnation point by application of the stress-optic rule. From both results, planar elongational viscosity was estimated. The planar elongational viscosity compared with the results measured by using 4-roll mill flow cell and squeeze flow cell and they showed good agreement.