The novel PZT micropumps with planar passive valves were successfully developed in this study. The periodically moving planar passive valves were actuated by the oscillatory flow which is due to the oscillation of a PZT membrane. The present micropump with planar passive valves provided higher diodicity (71%) with respect to previous valveless micropumps. From experimental results, reducing the mass of planar passive valves is useful to block the backward flow rapidly and decrease the switch time between pump mode and supply mode. In Type 1 device with planar passive valves of 13.6 μg, the optimum volume flow rate 266 μl/min was obtained at excitation voltage of 30 V and working frequency of 800 Hz. As the mass of passive valves were reduced to 10.6μg and 6.8 μg, the volume flow rates increased to 290 μl/min and 360μl/min, respectively. The results reveal that the performance of micropump was dominated by the mass of the moving parts. The transient motions of planar passive valves were observed by Micro-Particle-Image-Velocimetry (μ-PIV) and then the flow-rectified capabilities of the present device were analyzed. From the experimental results, the switching time decreased as the mass of moving part reduced, and thus the higher diodicty was obtained. This study indicates that this device fulfills the demands for microfluidic systems. Moreover, the present device can be applied to μ-TAS or lab-on-a-chip in the future.