Thin film heaters made of Ca-doped lanthanum chromite (LaCrO3) are fabricated by means of RF magnetron sputtering. Thin films of Ca-doped LaCrO3 show different heating characteristics under dc current drive for different purities of alumina substrate. In the case of a low purity (95.3%), LaCrO3 thin film heaters showed an increase of resistance with time. On the other hand, in the case of high purity (approximately 99.5%), the resistance was almost constant. It is speculated that impurities such as SiO2 contained in an alumina substrate enhance the migration of Ca atoms through the Pt electrode and increase the resistance because of the decrease of Ca atoms in the thin film. It is considered that the increase of resistance is caused by such a reaction.