A head mounted display apparatus and a distance measurement device are provided. The distance measurement device includes an image capturing device, a lens set, a position adjuster, and a controller. The position adjuster is configured to adjust positions of the image capturing device and the lens set. The position adjuster respectively adjusts the positions of the image capturing device and the lens set at a plurality of time points. The image capturing device respectively obtains a plurality of images of a target area at the plurality of time points. The controller accordingly obtains a separation distance between the lens set and the target area according to the plurality of images.