A step count detection unit detects one step (a step count) on the basis of the acceleration from an acceleration sensor, and outputs the detection result to an acceleration accumulation unit. The acceleration accumulation unit calculates, within a period of time corresponding to the one step detected by the step count detection unit, an acceleration cumulative value (simple posture pitch angle) by accumulating the acceleration detected by the acceleration sensor. The posture detection unit detects, on the basis of the acceleration cumulative value calculated by the acceleration accumulation unit, the posture of a portion for which the acceleration sensor is provided.
