A display apparatus assembly including: a display apparatus; and a speed measuring device that measures a movement speed of the display apparatus, wherein the display apparatus includes a glass-type frame that is mounted on a head of an observer and two image displaying devices for left and right eyes that are mounted in the frame, each of the image displaying devices includes an image forming device, an optical system that forms light output from the image forming device to be parallel light, and an optical device to which light output from the optical system is incident and in which the light is guided so as to be output, and a convergence angle is changed based on the movement speed of the display apparatus that is measured by the speed measuring device.