In this paper we suggest a high power CW mm-Wave source driven by a compact electron storage ring with modest size and energy. The source is working as a `power transformer' of a standard RF power into mm-waves via coherent radiation of fully bunched electron beam. The mm-wave power in a form of TEM Gaussian beam is generated in a high-field long period (high-K) helical wiggler. The wiggler provides for an effective energy exchange between the electron beam and the TEM mm-wave. The storage ring is designed to preserve electron beam with long (multi-hours) life-time. An optical resonator is used for feed-back to make the mm-wave FEL system an oscillator. The storage ring and mm-wave FEL provide for the bunching of the e-beam into mm-size buckets and for amplification of mm-wave inside the cavity.