The attachment device has a fixing member fixed to an attachment surface, first and second operating parts are configured to be manipulated from one side in the first direction parallel to the attachment surface, a first member fixed movably in the first direction relative to the fixing member, the first member being configured to move the display device in the first direction relative to the fixing member based on the operation amount of the first operating part, and a second member fixed rotatably relative to the first member, the second member being rotated based on the operation amount of the second operating part and being configured to move the display device in the second direction relative to the fixing member.