A user interface device configured to set and control a function of an electronic apparatus, the user interface device comprising: a body; a display unit configured to display screens with option groups of the function; a knob configured to rotate about an axis, wherein the knob is configured to be inserted into an inside of the body along the axis or to come out of the inside of the body along the axis according to a user's manipulation; a rotation sensor unit configured to sense an angle of rotation of the knob; a depth sensor unit configured to sense at least a depth among at least three depths of the knob; and a control unit, if the function is selected, configured to perform an option group transition of the selected function based on depth information according to the user's manipulation, and to control the display of a screen of an option group to which the option group transition is made, wherein the knob is further configured to be positioned in a maximum retraction depth and a plurality of different retraction depths, which are different from the maximum retraction depth, and to be rotated about the axis in each retraction depth so that at least one option value is selected among the option groups of the selected function respectively and sequentially, and wherein the display unit is further configured to be supplied with power in response to the knob being ejected from the maximum retraction depth and to display the screen with option groups of the function when the power is supplied, and wherein the knob further comprises a knob display unit configured to display a change in a depth of the knob according to the manipulation of the knob, which knob display unit comprises a plurality of lamps having concentric circles, wherein the control unit is configured to sequentially light the lamps (22a, 22b, 22c) of the knob display unit according to the depth information of the knob sensed by the depth sensor unit. a body; a display unit configured to display screens with option groups of the function; a knob configured to rotate about an axis, wherein the knob is configured to be inserted into an inside of the body along the axis or to come out of the inside of the body along the axis according to a user's manipulation; a rotation sensor unit configured to sense an angle of rotation of the knob; a depth sensor unit configured to sense at least a depth among at least three depths of the knob; and a control unit, if the function is selected, configured to perform an option group transition of the selected function based on depth information according to the user's manipulation, and to control the display of a screen of an option group to which the option group transition is made, wherein the knob is further configured to be positioned in a maximum retraction depth and a plurality of different retraction depths, which are different from the maximum retraction depth, and to be rotated about the axis in each retraction depth so that at least one option value is selected among the option groups of the selected function respectively and sequentially, and wherein the display unit is further configured to be supplied with power in response to the knob being ejected from the maximum retraction depth and to display the screen with option groups of the function when the power is supplied, and wherein the knob further comprises a knob display unit configured to display a change in a depth of the knob according to the manipulation of the knob, which knob display unit comprises a plurality of lamps having concentric circles, wherein the control unit is configured to sequentially light the lamps (22a, 22b, 22c) of the knob display unit according to the depth information of the knob sensed by the depth sensor unit.