PURPOSE: To make easier the integral combination or separation of a core tube and a sampler tube by a method in which the core tube and the sampler tube are each provided with oppositely directioned threads and screwed with a boring rod.

CONSTITUTION: A core tube 3 and a sampler tube 4, each having oppositely directioned threads, are screwed with a boring rod 1, and while turning the rod 1, excavation is made by the cutter 5 of the tube 3. After a pit is excavated to a given depth, the rod 1 is reversely turned, the tube 3 is separated from the rod 1, the rod 1 is brought down to penetrate the tube 4 into the ground, and the sample of soil is taken in the tube 4. Then, the rod 1 is turned to the left to remove it from the tube 4, the tube 3 is screwed with the rod 1 and penetrated into the ground, and lastly the tube 3 and the tube 4 are pulled up.