A portable device, comprising: a camera unit configured to capture an image in front of the portable device; a display unit configured to display a virtual image; and a processor configured to control the camera unit and the display unit, the processor further configured to: detect a marker object from the image, display the virtual image corresponding to the marker object based on a position of the marker object when the marker object is detected, detect a position change of the marker object, wherein when the position change is detected move the virtual image according to the position change; and obtain a moving speed of the virtual image or a moving speed of the marker object, wherein when the moving speed of the virtual image or the moving speed of the marker object is faster than a first reference speed, lower the moving speed of the virtual image to less than the first reference speed and display the virtual image with the lowered moving speed characterized in that the processor is further configured to stop displaying the virtual image when the moving speed of the virtual image or the moving speed of the marker object is faster than a second reference speed, wherein the second reference speed is faster than the first reference speed. a camera unit configured to capture an image in front of the portable device; a display unit configured to display a virtual image; and a processor configured to control the camera unit and the display unit, the processor further configured to: detect a marker object from the image, display the virtual image corresponding to the marker object based on a position of the marker object when the marker object is detected, detect a position change of the marker object, wherein when the position change is detected move the virtual image according to the position change; and obtain a moving speed of the virtual image or a moving speed of the marker object, wherein when the moving speed of the virtual image or the moving speed of the marker object is faster than a first reference speed, lower the moving speed of the virtual image to less than the first reference speed and display the virtual image with the lowered moving speed characterized in that the processor is further configured to stop displaying the virtual image when the moving speed of the virtual image or the moving speed of the marker object is faster than a second reference speed, wherein the second reference speed is faster than the first reference speed. detect a marker object from the image, display the virtual image corresponding to the marker object based on a position of the marker object when the marker object is detected, detect a position change of the marker object, wherein when the position change is detected move the virtual image according to the position change; and obtain a moving speed of the virtual image or a moving speed of the marker object, wherein when the moving speed of the virtual image or the moving speed of the marker object is faster than a first reference speed, lower the moving speed of the virtual image to less than the first reference speed and display the virtual image with the lowered moving speed characterized in that the processor is further configured to stop displaying the virtual image when the moving speed of the virtual image or the moving speed of the marker object is faster than a second reference speed, wherein the second reference speed is faster than the first reference speed.