A portable device comprising: a double sided display unit including a first display screen on a front side and a second display screen on a back side; a first touch sensor unit and a second touch sensor unit configured to respectively sense a first touch input for the first display screen and a second touch input for the second display screen; and a processor configured to control the double sided display unit, the first touch sensor unit and the second touch sensor unit, wherein the processor is further configured to: set a predetermined area of the second touch sensor unit; switch the second touch sensor unit to a ready-to-active state activating temporarily the predetermined area of the second touch sensor unit when the first touch input for the first display screen is sensed, wherein the predetermined area of the second touch sensor unit includes a predetermined point of the second display screen; display an indicator (62-1, 62-2) indicating specific point of the first display screen, wherein the specific point is symmetrical to the predetermined point of the second display screen; and switch the second touch sensor unit to an active state when the second touch input for the second display screen is sensed on the predetermined area including the predetermined point. a double sided display unit including a first display screen on a front side and a second display screen on a back side; a first touch sensor unit and a second touch sensor unit configured to respectively sense a first touch input for the first display screen and a second touch input for the second display screen; and a processor configured to control the double sided display unit, the first touch sensor unit and the second touch sensor unit, wherein the processor is further configured to: set a predetermined area of the second touch sensor unit; switch the second touch sensor unit to a ready-to-active state activating temporarily the predetermined area of the second touch sensor unit when the first touch input for the first display screen is sensed, wherein the predetermined area of the second touch sensor unit includes a predetermined point of the second display screen; display an indicator (62-1, 62-2) indicating specific point of the first display screen, wherein the specific point is symmetrical to the predetermined point of the second display screen; and switch the second touch sensor unit to an active state when the second touch input for the second display screen is sensed on the predetermined area including the predetermined point. set a predetermined area of the second touch sensor unit; switch the second touch sensor unit to a ready-to-active state activating temporarily the predetermined area of the second touch sensor unit when the first touch input for the first display screen is sensed, wherein the predetermined area of the second touch sensor unit includes a predetermined point of the second display screen; display an indicator (62-1, 62-2) indicating specific point of the first display screen, wherein the specific point is symmetrical to the predetermined point of the second display screen; and switch the second touch sensor unit to an active state when the second touch input for the second display screen is sensed on the predetermined area including the predetermined point.