A portable terminal includes an apparatus for improving motion detection capability. More particularly, the apparatus improves motion detection capability by changing a motion in a normal state according to a motion state or by changing a motion detection process in the portable terminal in order to avoid motion detection capability deterioration in the portable terminal are provided. The apparatus includes a terminal state determiner that determines a motion state of the terminal by receiving sensing information for determining the motion state, and a controller that changes a motion detection process according to the portable terminal's motion state determined by the terminal state determiner.