The JT-60 facility is now planning to replace the existing machine with a superconducting machine (JT-60SC) in order to proceed with advanced studies of steady state plasmas with high performance core conditions close to those of fusion reactor. A maximum plasma current of 4 MA and duration of 100 s are expected. Existing toroidal and poloidal field coils and vacuum vessel will be completely replaced. Since the present JT-60 system has been designed for a plasma current duration of 15 s, the coil and power supply systems need to be reconstructed to ones with a long pulse capability. This paper describes the new JT-60 machine and the design of the coil power supply system.