As a power source for practical micromachines such as in-pipe mobile micromachines using fluid power, micropumps having high power density are required. In this paper, a piezoelectric micropump using resonance drive is proposed and developed. It basically consists of a bellows as a flexible pump chamber with an additional mass, a piezoelectric actuator for oscillating the bellows and cantilever type of two check valves. Firs fly, an effectiveness of the proposed micropump is confirmed through a fabrication of the large model and basic experiments. Secondly, a micropump with the size of φ9x10 mm for practical application is fabricated. Next, frequency characteristics and load characteristics of pressure-dependent flow rate are experimentally investigated with various structural parameters for optimal design. Through those experiments, the optimal amounts of additional mass and valve thickness are experimentally obtained for stable and high performance of the micropump. The maximum flow rate of 80 mm3/s, maximum pumping pressure of 0.32 MPa and maximum power of 8.7 mW are obtained at the driving frequency of 2.0 kHz. Also the feasibility of the piezoelectric micropump using resonance drive is confirmed through a comparison with conventional micropumps on maximum power density.