A head-mounted display device, comprising: a first lens tube including a closed bottom and a first display part on the closed bottom, the first display part being for displaying a first image; a second lens tube including a closed bottom and a second display part on the closed bottom, the second display part being for displaying a second image; an adjustment mechanism including a first rod that extends from the first lens tube and a second rod that extends from the second lens tube and is rotatably connected relative to the first rod; and an image angle maintainer (81, 82, 83) that, in accordance with an angle of rotation of the first rod and the second rod of the adjustment mechanism, rotates the first display part relative to the first lens tube and rotates the second display part relative to the second lens tube to bring horizontal directions of the first display part and the second display part closer to an arrangement direction of the first lens tube and the second lens tube, wherein the image angle maintainer includes: a stator provided on an axis of rotation of the first rod and the second rod that does not rotate with the first rod and the second rod; characterized in that the image angle maintainer includes: a first rotor provided on the first display part that rotates with the first display part; a first belt that rotates the first rotor according to an amount of rotation of the first rod relative to the stator; a second rotor provided on the second display part that rotates with the second display part; and a second belt that rotates the second rotor according to an amount of rotation of the second rod relative to the stator. a first lens tube including a closed bottom and a first display part on the closed bottom, the first display part being for displaying a first image; a second lens tube including a closed bottom and a second display part on the closed bottom, the second display part being for displaying a second image; an adjustment mechanism including a first rod that extends from the first lens tube and a second rod that extends from the second lens tube and is rotatably connected relative to the first rod; and an image angle maintainer (81, 82, 83) that, in accordance with an angle of rotation of the first rod and the second rod of the adjustment mechanism, rotates the first display part relative to the first lens tube and rotates the second display part relative to the second lens tube to bring horizontal directions of the first display part and the second display part closer to an arrangement direction of the first lens tube and the second lens tube, wherein the image angle maintainer includes: a stator provided on an axis of rotation of the first rod and the second rod that does not rotate with the first rod and the second rod; characterized in that the image angle maintainer includes: a first rotor provided on the first display part that rotates with the first display part; a first belt that rotates the first rotor according to an amount of rotation of the first rod relative to the stator; a second rotor provided on the second display part that rotates with the second display part; and a second belt that rotates the second rotor according to an amount of rotation of the second rod relative to the stator. a stator provided on an axis of rotation of the first rod and the second rod that does not rotate with the first rod and the second rod; characterized in that the image angle maintainer includes: a first rotor provided on the first display part that rotates with the first display part; a first belt that rotates the first rotor according to an amount of rotation of the first rod relative to the stator; a second rotor provided on the second display part that rotates with the second display part; and a second belt that rotates the second rotor according to an amount of rotation of the second rod relative to the stator. a first rotor provided on the first display part that rotates with the first display part; a first belt that rotates the first rotor according to an amount of rotation of the first rod relative to the stator; a second rotor provided on the second display part that rotates with the second display part; and a second belt that rotates the second rotor according to an amount of rotation of the second rod relative to the stator.