A detection device includes an X-axis magnetic sensor, a Y-axis magnetic sensor, and a Z-axis magnetic sensor each having a sensing axis for detecting a geomagnetic azimuth and a sensor controlling semiconductor. The magnetic sensors are selected from those fabricated from the same wafer, each having the same structure, and directly mounted on the circuit substrate by directing the respective sensing axes of the magnetic sensors at different predetermined angles. Electrodes of the magnetic sensors for conducting the sensor controlling semiconductor are located in a parallel row at one side of the sensing surface.