Provided is an operating voltage scaling method for a portable terminal. The method includes, if reproduction of a moving image is requested, acquiring DYNamicity (DYN) of the reproduction-requested moving image, determining whether frame skipping is possible for the moving image according to the acquired DYN of the moving image, and if it is determined that frame skipping is possible for the moving image, supplying a low operating voltage to a controller of the mobile terminal to control the mobile terminal to operate with a low-speed clock, and reproducing the moving image while skipping a frame.