This case report describes a patient who developed positional vertigo after surgery for chronic otitis media on the right side. Canal wall up mastoidectomy was performed, and the stapes was moderately mobilized during removal of the inflammatory granulation tissues that were attached to it. Immediately after the surgery, positional vertigo developed. The patient showed weakly left-beating spontaneous nystagmus in a seated position. Examination of positional nystagmus revealed geotropic direction-changing positional nystagmus with a prolonged duration and weak intensity in a supine head-roll test, which may be caused by a change in inner ear fluids due to a disruption of inner ear membrane around the oval window or penetration of toxic materials into the labyrinth during surgery.