An electronic apparatus, comprising: a processing unit capable of setting a numerical value of a zoom adjustment state; a display control unit configured to display a knob that is movable on a slider in accordance with a user dragging operation as a setting screen of the numerical value; and an operation control unit configured to change the numerical value depending on a change of the position of the knob by the user dragging operation on the setting screen displayed by the control of the display control unit, the display position of the knob on the slider being changed with the change of a touch position of the user dragging operation; wherein when the user dragging operation is not started, the display control unit is configured to set a position of the knob in the center of the slider; when the user dragging operation on the knob is no longer performed, the operation control unit is configured to stop changing the numerical value immediately and, when a touch operation of the user dragging operation is no longer performed, the display control unit is configured to return the display position of the knob to the center of the slider in a predetermined time period; and wherein the electronic apparatus is a smart phone; characterized in that: the operation control unit is further configured to change the speed at which the numerical value is changed in accordance with the shift of the knob from the center of the slider so that the further the knob is shifted from the center of the slider by the user dragging operation, the faster the speed at which the operation control unit changes the numerical value. a processing unit capable of setting a numerical value of a zoom adjustment state; a display control unit configured to display a knob that is movable on a slider in accordance with a user dragging operation as a setting screen of the numerical value; and an operation control unit configured to change the numerical value depending on a change of the position of the knob by the user dragging operation on the setting screen displayed by the control of the display control unit, the display position of the knob on the slider being changed with the change of a touch position of the user dragging operation; wherein when the user dragging operation is not started, the display control unit is configured to set a position of the knob in the center of the slider; when the user dragging operation on the knob is no longer performed, the operation control unit is configured to stop changing the numerical value immediately and, when a touch operation of the user dragging operation is no longer performed, the display control unit is configured to return the display position of the knob to the center of the slider in a predetermined time period; and wherein the electronic apparatus is a smart phone; when the user dragging operation is not started, the display control unit is configured to set a position of the knob in the center of the slider; when the user dragging operation on the knob is no longer performed, the operation control unit is configured to stop changing the numerical value immediately and, when a touch operation of the user dragging operation is no longer performed, the display control unit is configured to return the display position of the knob to the center of the slider in a predetermined time period; and wherein the electronic apparatus is a smart phone; characterized in that: the operation control unit is further configured to change the speed at which the numerical value is changed in accordance with the shift of the knob from the center of the slider so that the further the knob is shifted from the center of the slider by the user dragging operation, the faster the speed at which the operation control unit changes the numerical value.