A navigation unit having a gyro sensor mounted thereon. The unit includes a mounting mechanism for changing the mounting direction of the gyro sensor so that the rotation detecting axis of the gyro sensor may be vertical, i.e. normal to a vehicle. In one embodiment, the navigation unit includes a support device for supporting the gyro sensor rotatably with respect to a casing. The gyro sensor may be supported in a rocking manner in the casing, and mounted to be changed between a first mounting direction and a second mounting direction perpendicular to the first mounting direction. In the preferred construction, the gyro sensor has a first pin and a second pin, and the casing has a first guide groove for receiving and guiding the first pin, and a second guide groove extending perpendicular to the first guide groove for receiving and guiding the second pin. The second guide groove provides a rocking center for the gyro sensor.