The quality of garlic productions and reduction of labor cost which are important to overcome price competition against import garlic. Improving to the quality of garlic production and reducing of labor cost, The garlic seed must be planted with the downward positioning of garlic seed root. This research was conducted to develop a crank-link mechanism for planting garlic seed with the downward positioning of garlic seed root. Computer simulation was conducted for developing a crank-link mechanism. A prototype of developing crank-link mechanism was manufactured and laboratory tests was performed. As results, Followings are achievements in range of plant depth = 50~70 (mm) with tolerance depth 3 mm, planting hole size = 45×50 (mm) with tolerance size 5 mm at planting speed 0.3 m/s.