A cradle for an on-vehicle navigation system using a portable terminal includes directional sensors, such as a gyro-sensor and an acceleration sensor, and a plate-shaped fixing unit for fixing the on-vehicle navigation system onto a desired surface inside a vehicle. The cradle further includes a support extending upwardly from the fixing unit, a fastening unit rotatably positioned on the support and receiving the portable terminal thereon, and a sensor unit rotatably coupled to the support and provided with a leveler in its uppermost end.