Though the spread of the touch screen devices is now revitalized, the Korean input methods in the touch screen devices are mostly the button input methods using keypads. Even though the button input methods are used with a touch screen, they still adopts the existing qwerty keyboard. It means that the existing methods can not be improved. This research suggests that the Korean input method which can be used in the portable terminals and the touch screen devices, for example, a smart phone which has a limited sized screen. It assigns every vowel a process which corresponds with the Korean invention theory and the vowel input method is to drag it. Through the mock experiments, we confirmed that the simplification of the Korean alphabet is more efficient than the existing methods, in the point of the speed of the Korean input.