To provide a salt contamination predicting apparatus to monitor an insulator contamination condition so as to predict salt contamination on an insulator.

A simulation insulator 2 consists of a material with an excellent electrical insulation property and a high water absorbing property. A salt contamination predicting apparatus is composed of an automatic water supply apparatus 6 to supply water to the simulation insulator 2, a high-voltage generator 7 to apply a high voltage, and contamination detecting circuits 8, 9. The simulation insulator 2 is located around an actual insulator to have the same salt contamination as to the actual insulator. As the simulation insulator 2 has a high water absorbing property, it keeps higher humidity than that of the actual insulator. Therefore, the simulation insulator 2 shows a salt contaminating phenomenon earlier and more remarkably than the actual insulator. A contamination predicting apparatus predicts salt contamination on the actual insulator by monitoring the phenomenon.