An object of the present invention is to provide a substance which is able to be an active ingredient for the improvement of dysfunction caused by nerve damage. An improving agent for dysfunction due to nerve damage of the present invention as a means for resolution thereof is characterized in that it comprises an endo-β-N-acetylglucosaminidase type enzyme which hydrolyzes an N-acetylglucosamide bond in a keratan sulfate backbone as an active ingredient. When the improving agent of the present invention is administered, clinical improvement is achieved in motor neuron dysfunction and sensory neuron dysfunction such as neuropathic pain represented by a pain caused by allodynia and hyperalgesic reaction of the object to be treated.
