Whether one of a users feet has touched the ground is detected on the basis of detection values from an acceleration sensor. In a single walking cycle, a period in which the user is standing on a first (the second) foot from a time when a detecting member detects that the first (second) foot has touched the ground to a time when the detecting member detects that a second (first) foot has touched the ground is defined as a first (second) stance period. A representative value for the detection values for each of the first and the second stance period is calculated on the basis of the detection values detected by the acceleration sensor. Whether or not a walking is an ascending (descending) walking is determined on the basis of a comparison result between the calculated representative values for the first and the second stance period.
