The invention relates to a soil improvement appliance, including a nozzle which has a gas spout provided with compressed air and is disposed on front end of a pipe that is connected with a compressed air supply device, capable of ejecting compressed air from the gas spout of the nozzle to dig holes on soil. The soil improvement appliance of this invention is characterized in that the nozzle is featured that the nozzle outer periphery at the maximum diameter is more prominent than outer diameter of the pipe, in such a manner that the ratio of the circular area calculated at the nozzle maximum diameter minus an area calculated at the pipe outer diameter to an area of the air spout of the nozzle is more than five, and the nozzle is substantially located at a straight line registered with the slightly linear pipe in the digging direction.本發明之土壤改良器具係在與壓縮空氣供給裝置連接的管件前端部具有具備壓縮空氣的噴氣口之噴嘴,從噴氣口噴出壓縮空氣而將土壤挖掘為孔狀的土壤改良器具,其特徵為:使用以(噴嘴最大外徑為直徑所算出的圓面積-從管件外徑所算出的面積)/噴嘴噴氣口面積成為5以上的方式,使噴嘴外周部的最大外徑比管件外徑更為鼓出,並位於與朝向挖掘方向之略呈直線狀的管件大約同一直線上之噴嘴。1...管件2...噴氣口3...噴嘴4...溝
