To propose a new method for accurately detecting the start of walking.

A pedometer 1 detects a pitch angle as the attitude angle of a user as a walker based on the detection result of a gyro sensor 43. Then, it is determined whether or not synthetic acceleration to be obtained by synthesizing the detection results of an acceleration sensor 41 exceeds prescribed threshold acceleration, and when the synthetic acceleration exceeds the threshold acceleration, it is estimated that walking has been started, and otherwise, the start of walking is estimated based on the temporal change of the pitch angle.