A mobile device comprising: an e-paper display unit configured to display contents; an input signal receiving unit configured to detect an input signal and transmit the detected input signal to a processor; and the processor configured to control the e-paper display unit and the input signal receiving unit, wherein the processor is further configured to: switch the mobile device from an active mode to a first standby mode when a lack of a touch input signal is detected for a predetermined time, wherein the first standby mode is a mode displaying a first image on the e-paper display unit, maintaining the first image displayed on the e-paper display unit and disabling detecting of a touch input signal for the displayed first image, switch the mobile device from an active mode to a second standby mode when a first standby switching signal is detected within the predetermined time, wherein the second standby mode is a mode displaying a second image on the e-paper display unit, maintaining the second image displayed on the e-paper display unit and disabling detecting of a touch input signal for the displayed second image, switch the mobile device to a first lock mode when a standby release signal is detected in the first standby mode, wherein the first lock mode is a mode displaying an unlock interface on the first image and detecting an unlock signal for the unlock interface on the first image, switch the mobile device to a second lock mode when the standby release signal is detected in the second standby mode, wherein the second lock mode is a mode displaying the unlock interface on the second image and detecting the unlock signal for the unlock interface on the second image, and switch the mobile device to an active mode when the unlock signal is detected in the first lock mode or the second lock mode. an e-paper display unit configured to display contents; an input signal receiving unit configured to detect an input signal and transmit the detected input signal to a processor; and the processor configured to control the e-paper display unit and the input signal receiving unit, wherein the processor is further configured to: switch the mobile device from an active mode to a first standby mode when a lack of a touch input signal is detected for a predetermined time, wherein the first standby mode is a mode displaying a first image on the e-paper display unit, maintaining the first image displayed on the e-paper display unit and disabling detecting of a touch input signal for the displayed first image, switch the mobile device from an active mode to a second standby mode when a first standby switching signal is detected within the predetermined time, wherein the second standby mode is a mode displaying a second image on the e-paper display unit, maintaining the second image displayed on the e-paper display unit and disabling detecting of a touch input signal for the displayed second image, switch the mobile device to a first lock mode when a standby release signal is detected in the first standby mode, wherein the first lock mode is a mode displaying an unlock interface on the first image and detecting an unlock signal for the unlock interface on the first image, switch the mobile device to a second lock mode when the standby release signal is detected in the second standby mode, wherein the second lock mode is a mode displaying the unlock interface on the second image and detecting the unlock signal for the unlock interface on the second image, and switch the mobile device to an active mode when the unlock signal is detected in the first lock mode or the second lock mode. switch the mobile device from an active mode to a first standby mode when a lack of a touch input signal is detected for a predetermined time, wherein the first standby mode is a mode displaying a first image on the e-paper display unit, maintaining the first image displayed on the e-paper display unit and disabling detecting of a touch input signal for the displayed first image, switch the mobile device from an active mode to a second standby mode when a first standby switching signal is detected within the predetermined time, wherein the second standby mode is a mode displaying a second image on the e-paper display unit, maintaining the second image displayed on the e-paper display unit and disabling detecting of a touch input signal for the displayed second image, switch the mobile device to a first lock mode when a standby release signal is detected in the first standby mode, wherein the first lock mode is a mode displaying an unlock interface on the first image and detecting an unlock signal for the unlock interface on the first image, switch the mobile device to a second lock mode when the standby release signal is detected in the second standby mode, wherein the second lock mode is a mode displaying the unlock interface on the second image and detecting the unlock signal for the unlock interface on the second image, and switch the mobile device to an active mode when the unlock signal is detected in the first lock mode or the second lock mode.