To provide a technique useful for an in-process inspection method for the conductivity of a conductive plastic molding or the like, saying in concretes, to provide a method of inspecting easily and highly precisely the conductivity without providing an elaborate electric terminal or the like onto an inspecting object.

A high frequency magnetic field is generated by making a high frequency current flow in a coil inside a sensor, a conductivity measuring object is laid within the magnetic field to make an eddy current flow in the object by electromagnetic induction, and conductivity of the measuring object is inspected, without providing directly an electric terminal or the like onto the object, based on the change of an impedance of the coil inside the sensor therein.