The present invention relates to an agent for preventing and/or treating diabetic neuropathy comprising a 2-[(substituted-inden-7-yloxy)methyl]morpholine of the formula (I) or a pharmaceutically acceptable salt thereof as an active ingredient. The invention is useful for providing an excellent agent for preventing and/or treating diabetic neuropathy, and particularly useful for providing an agent for preventing and/or treating diabetic motor neuropathy (such as muscle weakness disorder (such as muscle weakness disorder with inability to walk independently)), diabetic sensory neuropathy (such as paresthesia (such as vibration perception abnormality), allodynia, hypoesthesia (such as numbness of extremities or cold sensation), or pain), or diabetic autonomic neuropathy (such as stool abnormality (such as constipation or diarrhea), urination disorder, impotence, orthostatic hypotension, sudomotor dysfunction, abnormal heart rate variability, or delayed gastric emptying). Further, the invention is particularly useful for providing an agent for improving pathophysiology of diabetic neuropathy.