Electrochromism of cobalt and zinc naphthalocyanines (CoNc, ZnNc) was investigated in thin films vacuum-deposited on indium tin oxide substrates. The CoNc film exhibited color changes from original green to purple both upon reduction and oxidation, and the ZnNc film exhibited a color change from green to brown only upon oxidation. The electrochromic reduction was a reversible process depending on an electroactivity of the central Co metal, and the electrochromism was attributed to a transition from a reduced state related to the Co(I) center to a pi*-state of the Nc-ligand. On the other hand, the electrochromic oxidation irreversibly occurred at the Nc-ring ligand. The ring-oxidation was stably maintained by a retention of incorporated anions, which caused a film restructuring accompanied with a discorder of molecular stacking from the original a-polymorphic form to an amorphous structure in the oxidized state.