Micro-weighing device by using null balance method is being essential part in fields of high-technology industries such as precision semiconductor industry, precision chemistry, biotechnology and genetics etc. Also, requirements for high resolution and for large measurement range increase more and more. The performance of the micro-weighing device can be determined by the mechanism design and analysis. The analytical design method has been proposed for the performance improvement such as resolution, measurement range and fast response. The 2-stage displacement amplification is designed to overcome the limit of conventional force transmitting lever. The parallel spring is designed for the measurement result independent of the input force position variation. Also, the natural frequency of mechanism is analyzed for the fast response. After each analysis, optimal design has been carried out. To verify the analysis and design result, characteristics experiments had been carried out after construction. Finally, the system had been controlled.