PURPOSE: To sample a liquid freely through remote operation by sampling and inspecting the circumferential liquid at an optional position without fixing a sampling device which detects radiation leakage in a pit wherein a radioactive material, etc., is stored at a position for the sampling.

CONSTITUTION: The sampling device 10 mounted on a traverser moves left and right, and forth and back freely to be set on the top surface of a prescribed storage chamber 3. On the reverse surface of the base 11 of this device 10, a sampling monitor chamber 12 is arranged and in the monitor chamber 12, a monitor body guide 13 having the same shape and fitting position relation with a guide 5 for storage installed in the storage chamber 3 is installed. In said monitor chamber 12, there is specific clearance with the monitor body guide 13 and an opening part 15a is provided internally between monitor body guides 13 adjoining to each other in the clearance; and the sampling monitor body 15 moving up and down by rolling on the surface of the monitor body guide 13 by guide rollers installed on both side surfaces is suspended by being fixed to the lower end part of a sampling and suspending tube 16. The sampling monitor boty 15 is lowered to suck a sampling liquid at the circumference of a desired canister.