To provide a non-destructive method and a system for surveying geological conditions, which can solve various drawbacks caused by employing an inner container, without spoiling benefits of known technologies.

In the method, a pressure bulkhead 1 is installed so that its aperture section 6 is in close contact with the ground, and air in the pressure bulkhead 1 is sucked to reduce the pressure, thereby sampling a fluid sample 19 such as underground air, groundwater or the like. In the sampling step of the fluid sample, while air 18 in the outside region in the pressure bulkhead 1 is sucked by a suction system 2, air 19 in the inside region is sucked by another suction system 3.