PURPOSE: To obtain sure and simple execution of a rock bolt for timbering in the upward direction in a job site of tunnel construction or of bed rock cutting work.

CONSTITUTION: An excavation hole 2b is made upward with respect to a natural ground 2, and a hollow rock bolt 5 is inserted into this excavation hole 2b. The excavation hole 2b is then filled with an injection material 6 such as mortar via a filling pipe 9, beginning with a space around the rock bolt 5. With this filling, air 12, which exists within the excavation hole 2b, is removed to the outside via both a porous sealing member 10 and an air passage 5b. With this contrivance, the rock bolt 5 can firmly be fixed to the natural ground 2 via the injection material 6, which is solidly hardened by this time. Thus, it becomes unnecessary to provide an air vent pipe separately from the rock bolt 5.