Herpes zoster can involve the variable peripheral nervous system but there have been few reports about plexopathy by the herpes zoster. We report a 54-year-old man with left leg weakness soon after herpes zoster in the left leg. His electrophysiological findings were consistent with the left lower lumbosacral plexopathy. It was concluded that herpeszoster can be considered to be one of the rare causes of the lumbosacral plexopathy.