A portable measurement system for ambient vibration test of building has been developed. The motive of the development is to know the gereral trends of vibration characteristics of many actual buidings. The equipment of the system consists of transducers, amplifiers, A/D converter and handheld micro-computer. The advantages of the system are high portability, quick setting of the equipment, and immediate analysis of the records at the field, without any work in laboratory. The analysis gives the natural periods and damping coefficients for translational and torsional vibrations. The weight of the equipment for low-rise buiding is only 9 kg and that for highrise building is 20 kg. They are capable of operating by only dry battery. The vibration characteristics of buildings in Tokyo, Yokohama and Mexico City were measured by this system. The results show large difference on rigidity of buildings in Japan and Mexico.