We have demonstrated the usefulness of giant magnetoresistance (GMR) in Co/Cu superlattices for practical application to the magnetic rotation sensor. Optimized Co/Cu superlattices have been fabricated into sensors with appropriate passivation layers. The sensor output changes more than 20%, synchronizing the rotation of the magnet rotor. It is remarkable that there is no significant degradation of the GMR sensors even after they are left in the atmosphere of the air at 150 degrees C for 1000 h. This confirms the high reliability of the GMR sensors and promises that they can be used in automobiles and aircraft under severe conditions.