A scanning method for determining the touch position of a touch input apparatus is disclosed. First of all, a first exposure process on light sensors of the touch input apparatus by light emitting device of the touch input apparatus is performed. Then the light sensors are scanned. A light sensor generating a signal with a maximum value is located. A region of partial scan of the light sensors is determined according to the position of the light sensor generating the signal with the maximum value. A second exposure process is performed on the light sensors. Then the light sensors within the region of partial scan are scanned. A light sensor generating a signal with a maximum value within the region of partial scan is located and a next region of partial scan is determined. The maximum value of the signal is calculated and the maximum value of the signal is compared to a predetermined value to determine whether the maximum value is higher than the predetermined value.