To provide an improved ground testing method capable of speedily verifying the quality of improved ground and facilitating rework to be executed in the case that the quality of improved ground falls to a reference value or below and to provide an unsolidified sampler suitable for the testing method.

After the execution of the improvement work of improved ground, an unsolidified sampler at any depth is collected when the improved ground (g) is in an unsolidified state. Compaction test is performed on the unsolidified sample after its collection to estimate its final strength of a material age of four weeks on the basis of results of the compaction test. The unsolidified sampler includes a plurality of mold cans 3 to be filed with an unsolidified sample; a plurality of samplers 2 for each housing the mold cans 3; a long main rod 1 to which the plurality of samplers 2 are mounted longitudinally at regular intervals; and a pressing means for pressing the unsolidified sample in the mold cans 3. The pressing means includes a pneumatic cylinder 4 for vertically moving a pressing plate 6 via an operating rod 5. By vertically moving the pressing plate 6, the unsolidified sample can be filled in the mold cans 3.