In an exercise support device of the present invention, acceleration signals in three axis directions including vertical, longitudinal, and lateral directions corresponding to the motion of a user performing exercise of cyclically moving feet are obtained, and a first maximum value in one cycle of a foot movement in the vertical acceleration signal is obtained. Subsequently, a search is made for first and second change points related to foot landing and takeoff motions in a composite acceleration signal obtained by combining acceleration signals in at least two axis directions, in forward and backward directions of the time point of a second maximum value of the composite acceleration signal, within the cycle. Then, a time period between the first and second change points is obtained as a change point interval, and a foot landing period while exercising is calculated based on the first maximum value and the change point interval.