The present invention is to provide a technology capable of planting seedlings in soil in planting ground such as
dry land and allowing the
seedling to root securely and grow without artificially supplying water continuously. Not only is a
seedling fixed inside an upper opening portion of a tube having a length to a
deep water-containing layer in the planting ground but also a growing medium is put inside the tube at a
hardness that allows the root of the
seedling to grow long downward, and the root of the seedling is allowed to grow below the tube, thereby obtaining the seedling having a long root. A vertical hole having approximately the same
diameter as that of the tube is dug in the ground of the planting ground until reaching a soil layer having
water quality and water quantity necessary for growth of
plant, the seedling having the long root is buried in the vertical hole together with the tube, thereby planting the seedling in the planting ground.