This presentation describes a new valveless micropump for bidirectional use. The micropump was fabricated by bonding a fluidic channel and a membrane actuator. The fluidic channel was etched on a glass substrate and the membrane actuator was made on a silicon wafer. The membrane is actuated by a piezoelectric ceramic (PZT) plate so that the membrane generates blowing and suction flows successively along an oblique channel which is connected to the main channel. A blowing flow from an oblique channel into the main channel generates forward flow in downstream, while a suction flow generates the smaller reverse flow in downstream. Therefore, the overall flow in the main channel has a downstream flow and it can have a directional characteristic when two oblique channels are used. The performance of the micropump depends on the geometry of the fluidic channel, driving frequency and voltage of the actuator. The geometry of the micropump was optimized by numerical analysis and the performance test was done under various operating conditions. The maximum flow rate was 323?l/min and the maximum back pressure was 294 Pa when the membrane actuator of 10mm?10mm was driven at 130 Hz and 385V.