An exercise supporting device including a detecting section which repeatedly detects motion data relative to the exercise motion status of a user during the exercise motion; an analyzing and judging section which obtains, based on the motion data, a first motion information value corresponding to the user's moving speed and a second motion information value corresponding to the user's footstep count per unit time or footstep width at each time the detecting section detects the motion data, and judges whether the first motion information value is out of a first numerical value range and whether the second motion information value is out of a second numerical value range; and an output section which, when at least one of the motion information values is judged as being out of the relevant numerical value range, performs an informing operation regarding this motion information value.