To provide an in-hole permeability coefficient measuring device and method that can provide a testing section for measuring a permeability coefficient, in a desired section in a borehole with simple constitution.

The in-hole permeability coefficient measuring device 10 comprises a packer rod 20, an extension rod 30, connection nuts 40, and extension hoses 50 for extending various hoses installed in the rod etc., as components. The packer rod 20 and the extension rod 30 are combined and connected by the connection nuts 40 to arrange packers 26 to partition predetermined sections inside the borehole 60. The extension hoses 50 are installed in the borehole 60 being respectively connected to the various hoses installed inside the borehole 60 from the outside of the borehole 60.