The invention relates to a gaseous mercury capturing device which comprises a pipe and a gold wire arranged in the pipe through a limiting support, wherein the melting point of the limiting support is higher than the melting point of the gold wire; and due to the construction of the limiting support, the gaseous mercury can be in contact with the gold wire, so that the gaseous mercury can be adsorbed by the gold wire. According to the invention, the possibility of the change in density on each position caused by the deformation of the gold wire can be controlled and the consistent density of the gold wire on each position can be guaranteed, so that the capability of adsorbing and releasing the mercury after the repeated use of the gaseous mercury capturing device can be guaranteed and the use times of the mercury capturing device can be increased; the reproducibility is high; the analysis data is true and reliable; the reliability of geological interpretation is promoted; the volume is small; and the gaseous mercury capturing device is portable.