A humidity state at a distal end portion of an endoscope internal space can be reliably estimated without enlarging the diameter of an endoscope insertion part.In a humidity detecting device detecting humidity of an internal space of an endoscope, leakage currents of an imaging device and a peripheral circuit of an electric board disposed at a distal end portion of the internal space of the endoscope are detected and a humidity state of the internal space of the endoscope is determined based upon the detected leakage currents.
