According to the present invention, a signal representing acceleration and a signal representing atmospheric pressure are acquired by an acceleration sensor and an atmospheric pressure sensor worn by a subject being measured (S1). On the basis of the signal representing acceleration, it is detected that the subject being measured is walking, and a signal representing the gait cycle of the subject being measured is acquired (S2). On the basis of a signal representing the gait cycle, the number of steps taken by the subject being measured is counted (S3). For a unit period composed of a predetermined number of gait cycles, signals representing atmospheric pressure values are averaged, and a signal representing an averaged atmospheric pressure value for each unit period is created (S4). The change in averaged atmospheric pressure value from a first unit period to a second unit period is calculated, and on the basis of the change, it is determined whether walking by the subject being measured in the second unit period involves ascent or descent of stairs (S5). According to the result of the determination, the number of steps representing ascent or descent of stairs by the subject being measured, of the counted number of steps taken by the subject being measured, is calculated (S6).Selon la présente invention, un signal représentant une accélération et un signal représentant la pression atmosphérique sont acquis par un capteur daccélération et un capteur de pression atmosphérique portés par un sujet mesuré (S1). Sur la base du signal représentant laccélération, il est détecté que le sujet mesuré est en train de marcher et un signal représentant le cycle de démarche du sujet mesuré est acquis (S2). Sur la base dun signal représentant le cycle de démarche, le nombre de marches montées ou descendues par le sujet mesuré est compté (S3). Pendant une période unitaire composée dun nombre prédéterminé de cycles de démarche, la moyenne des signaux représentant les valeurs de pres
