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A portable gamma-ray monitor composed of a compact electrically cooled germanium detector and a mini-MCA system was developed for in-situ gamma-ray monitoring with very fast starting time and easy operation. This detector may be used mainly in an accident, an emergency, a fast inspection and an easy analysis because the starting time of the Ge detector is 51 minute. The size of Ge detector is 10.2cmφ × 39.3cm and the weight 5.2kg. A small Stirling refrigerator can cool down a 14cm3 planar-type high purity Ge detector with the relative detection efficiency of 1% automatically with a low consuming driving power supply. After cool down, coming gamma rays are measured and analyzed repeatedly by a mini-MCA system with a very small hand held computer. The energy resolution of the detector is 2.46 keV at gamma ray of 1.33MeV. Consequently, a user can comfortably analyze gamma-rays spectrum with decision of the nuclide and its quantitative analysis by watching the display on the hand held computer.