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Milky Way Galaxy is thought to be a spiral galaxy.Since recent observations have revealed the existence of bar at the Galactic center, now we understand the our Galaxy as the barred galaxy.However, it is hard to understand the detailed structure of our Galaxy because we are in.A few years ago, an annual parallax of Galactic maser sources had been measured by the Very Long Baseline Interferometry (VLBI).The measured distance by VLBI was 2 kpc which is larger than results of the astrometric satellite, HIPPARCOS.Since over l,000 Galactic maser sources are distributed at the whole Galaxy, the detailed structure and dynamics of the our Galaxy will be understood by the VLBI astrometric observation. We selected the 2nd Galactic quadrant as our target area, which is called the outer Galaxy.We surveyed H2O maser sources by the Very Large Array (VLA),Effelsberg and Nobeyama radio telescope.We chose one of H2O maser sources from our database, and performed the VLBI astrometric observation by the Very Long Baseline Array (VLBA).We have detected the small annual parallax and then have estimated the distance from the Sun to the target source of 6.0 kpc which is corresponding to the Galactocentric distance of 13.4 kpc.Since the target source is one of the most distant H2O maser sources from the Galactic center, perhaps the object may be around the edge of optical stellar disk of our Galaxy.We have also found the flat Galactic rotation curve and thus confirmed the existence of the dark matter in the our Galaxy. Finally, the East Asia VLBI Network (EAVN) will start within next few years. The EAVN is unique VLBI network as well as the VLBA and European VLBI Network (EVN).We can perform VLBI astrometric observation for other Galactic maser sources by the EAVN.Moreover, the EAVN will play an important role as ground based radio telescopes of the VSOP-2.We are also planing the VSOP-2 astrometry for the most distant objects in our Galaxy.