This paper presents high-performance millimeter-wave passive devices using MEMS technology. The purpose of this paper is to show the possibility of MEMS technology as an enabling technology for millimeter-waves. The loss and cost issues, which have been the inherent barrier for commercialization of mm-waves, can be solved by RF MEMS technology. Successful demonstrations of MEMS technology for mm-waves include novel CPW transmission lines, digital impedance tuners, analog tunable band-pass filters, reconfigurable low-pass filters, V-band digital distributed phase shifters and 2-D mechanical beam-steering antennas. All these circuits were implemented for 30-65 GHz frequency range, and show the state-of-the-art performance, which is beyond the limit set by the conventional technology.