A portable device comprising: a tilt sensor unit configured to obtain an amount of tilt of the portable device, wherein the tilt refers to an angle (θ) between a reference ground surface and the portable device; a display unit attached to a front surface of the portable device and configured to sense a touch input on the front surface of the portable device and configured to display an image, wherein the rear surface of the portable device is curved to allow tilting or rocking of the device when the device is placed on a surface and the front surface of the display unit faces upwards, so that a predetermined touch input on a front surface of the portable device causes a tilting or a rocking of the portable device; and a processor configured to control the tilt sensor unit, and the curved display unit, characterized in that the processor is further configured to: when providing a landscape mode with regard to an application being currently executed, switch from the landscape mode to a portrait mode (3030-1, 3030-2) when the tilt of the portable device is detected without a first touch input which is the predetermined touch input and the amount of the tilt exceeds a first threshold (θ1), and switch from the landscape mode to the portrait mode (3030-1, 3030-2) when the tilt of the portable device is detected along with the first touch input that causes the tilting or the rocking of the portable device and the amount of the tilt exceeds a second threshold (θ2), wherein the second threshold (θ2) is less than the first threshold (θ1). a tilt sensor unit configured to obtain an amount of tilt of the portable device, wherein the tilt refers to an angle (θ) between a reference ground surface and the portable device; a display unit attached to a front surface of the portable device and configured to sense a touch input on the front surface of the portable device and configured to display an image, wherein the rear surface of the portable device is curved to allow tilting or rocking of the device when the device is placed on a surface and the front surface of the display unit faces upwards, so that a predetermined touch input on a front surface of the portable device causes a tilting or a rocking of the portable device; and a processor configured to control the tilt sensor unit, and the curved display unit, characterized in that the processor is further configured to: when providing a landscape mode with regard to an application being currently executed, switch from the landscape mode to a portrait mode (3030-1, 3030-2) when the tilt of the portable device is detected without a first touch input which is the predetermined touch input and the amount of the tilt exceeds a first threshold (θ1), and switch from the landscape mode to the portrait mode (3030-1, 3030-2) when the tilt of the portable device is detected along with the first touch input that causes the tilting or the rocking of the portable device and the amount of the tilt exceeds a second threshold (θ2), wherein the second threshold (θ2) is less than the first threshold (θ1). when providing a landscape mode with regard to an application being currently executed, switch from the landscape mode to a portrait mode (3030-1, 3030-2) when the tilt of the portable device is detected without a first touch input which is the predetermined touch input and the amount of the tilt exceeds a first threshold (θ1), and switch from the landscape mode to the portrait mode (3030-1, 3030-2) when the tilt of the portable device is detected along with the first touch input that causes the tilting or the rocking of the portable device and the amount of the tilt exceeds a second threshold (θ2), wherein the second threshold (θ2) is less than the first threshold (θ1).