Disclosed is a display apparatus including: a display; an input comprising circuitry configured to receive a key moving command for moving between keys of an on-screen keyboard displayed on the display and a key-group selecting command for selecting a key group of the on-screen keyboard; and a processor configured to control a user interface (UI) of the on-screen keyboard, the keyboard comprising a first key group including keys=corresponding to a plurality of letters and a second key group including keys=corresponding to a plurality of functions, to be displayed on the display, to control an input marker moving between first keys of the first key group in response to the key moving command and at least one dummy marker moving between second keys of the first key group to be displayed if the first key group is selected by the key-group selecting command, to control an input of the first key to be made if a first key corresponding to the input marker is selected, to control a function marker moving between keys of the second key group in response to the key moving command to be displayed if the second key group is selected by the key-group selecting command, and to control a function of a key to be implemented if the key corresponding to the function marker is selected.