Orbital apex syndrome (OAS) is a rare disease. One of the causes of OAS is herpes zoster ophthalmicus (HZO). A 73-year-old man developed herpes zoster around the right eye, and oral amenamevir treatment was given for seven days. The right eyelid ptosis was observed on the third day, and right eye movement was restricted in all directions on the ninth day. His eyesight was also poor, and he was diagnosed with OAS associated with HZO. Cerebrospinal fluid examination revealed mononuclear cell increase; however, VZV-DNA was not detected. Intravenous infusion of acyclovir and oral prednisolone administration were started. Two weeks after the start of treatment, ptosis, eye movements, and visual acuity improved. If HZO is found, it is necessary to consider the possibility of developing OAS.