Electrical properties of electrochromic (EC) InN thin films prepared by rf ion plating were studied. There was a correlation between the electrical properties and the electrochromism in the InN films, particularly, carrier concentration changes were responsible for the electrical resistivity changes of the films due to the electrochromism. These carrier concentration changes were caused by chemisorbed hydroxyl groups and protons. From these results, it was proved that the carrier concentration changes of the InN films was responsible for the electrochromism in the visible and near-infrared region.