A head-mounted display apparatus includes an image display device, a wearing device with which the image display device is worn on a head of an observer, and an attachment member with which the image display device is attached to the wearing device. The attachment member is capable of adjusting a position of the image display device relative to the wearing device independently in a first direction and in a second direction, the first direction being defined by a virtual line connecting centers of eyes of the observer, the second direction being perpendicular to the first direction and extending vertically with respect to the observer.