Because the main trunks of the external carotid artery and maxillary artery are well protected from blunt trauma and superficial penetrating wounds through their course, traumatic aneurysms on these arteries are extremely rare. A 75-year-old woman had struck her occipital region against a door but there was no trauma to the mandibuloauricular region. After 1 month, she noticed a pulsatile mass below her right auricle. At operation an aneurysm was found to be located just distal to the origin of the maxillary artery.