A multi-information-layer optical disk system using electrochromism for layer selection has been studied. The advantages of this disk system are its large capacity, high sensitivity in recording, and use of a relative simple hardware. Reading and writing on an electrochromic information layer were successfully performed, and the results suggested an increase in transmittance and the degradation of electrochromism in the recorded area. This fact demonstrates the feasibility of recording on electrochromic layers and the electrical layer selection in the proposed multilayer disk. Also a disk evaluation apparatus was developed by installing an apparatus using ball bearings for voltage transfer to a multilayer disk, and voltage application to a disk was confirmed.