1. A mobile terminal apparatus, comprising: a magnetic sensor which detects three-axis components of a terrestrial magnetism vector; a tilt angle sensor which detects acceleration components in three-axis directions; a processing unit which is connected to the magnetic sensor and the tilt angle sensor, and which determines azimuth by performing coordinate transformation on the terrestrial magnetism components detected by said magnetic sensor, based on a detection result of said tilt angle sensor, wherein said processing unit detects acceleration components of a frequency in a predetermined range, based on a detection result along an axis among the axes of said tilt angle sensor which most approximates a gravity axis, and counts the number of user's steps.