A mobile terminal device for a positioning system based on a magnetic field map and a method thereof, are provided. The mobile terminal includes a memory configured to store a magnetic field map including magnetic field values at positions. The mobile terminal further includes a magnetic field sensor configured to measure a magnetic field value at a position of the mobile terminal. The mobile terminal further includes an inertial measurement unit (IMU) sensor configured to measure an acceleration value and a gyro value of the mobile terminal. The mobile terminal further includes a processor configured to determine the position of the mobile terminal based on the magnetic field map, the magnetic field value, the acceleration value, and the gyro value.