This application relates to a mechanical button apparatus that includes a body where an upper portion thereof is closed and a lower portion thereof is opened and a bottom plate attached on a display screen of a display apparatus to cover the opened lower portion. The body includes an aperture member including a wing set expanded or contracted in a rotation direction of the body. The body also includes a photovoltaic (PV) cell array substrate including a PV cell configured to generate power for charging a battery and an optical sensor configured to convert light signals, reflected by the expanded or contracted wing set, into electrical signals. The body further includes a circuit substrate configured to operate with the power charged into the battery, calculate number of rotation manipulations of the body by using the electrical signals, and transmit the calculated number of rotation manipulations to the display apparatus.