AbstractIn order to obtain the time evolution of the electron temperature in JT-60U plasmas, an electron cyclotron emission measurement system with fast time (of the order of microseconds) and high spatial (of the order of centimetres) resolution has been developed. The operation and data acquisition of the system and preliminary data analysis are made automatically. For precise measurement of the electron temperature profile it is important to correct the shift due to relativistic down-shift frequency in present-day tokamak plasmas.