Maxillary sinus mucocele can occur due to many medical factors such as chronic infection, allergic sinonasal disease, trauma, and previous surgery. However, it occurs mainly after Caldwell-Luc operation, usually more than 10 years after surgery. There are a few cases of maxillary sinus mucocele with ocular symptoms. Also, a case causing ocular symptoms because of invasion to the orbital floor is rare. Therefore, we report a case of a 55-year-old male patient who underwent Caldwell-Luc operation about 30 years ago. Then, symptoms such as exophthalmos, diplopia, and visual disturbance developed suddenly 3 months prior to admission. Computed tomography showed a cyst invading the orbital floor which resulted in eyeball deviation. The orbital floor defect measured approximately 2.5×3.3 cm. Maxillary sinus mucocele was removed through an endoscopic approach. After this, we reconstructed the orbital floor through a subciliary incision. Observation was carried out after three years, and ocular symptoms such as diplopia and exophthalmos did not recur.