To provide an economical packer for a rock bolt with good execution by housing one or the other of a two-liquid mixture type urethane-based foaming chemical in two chemical storage vessel stored in the inside of a cylindrical bag body respectively.

Two breakable chemical storage vessels 3, 4 are provided in the inside of a cylindrical bag body capable of being mounted to the outer peripheral part of a rock bolt 5 and having water passing. Next, one of a two- liquid mixture type urethane-based foaming chemical is stored to one chemical storage vessel 3, a rock bolt 5 mounting the packer for the rock bolt 1 on a root part is disposed in an oblong hole 31 drilled in soil and natural ground 30. In the state, both the chemical storage vessels 3, 4 in the packer 1 are broken to mix both of the two-liquid mixture type urethane-based foaming chemical, so that the bedrock of the circumference of the oblong hole 31 is consolidated. As a result, a pump or a mixer is unnecessary, and the economical packer for the rock bolt 1 with good execution can be obtained.