A chiller's performance tester includes two flowrate sensors, four temperature sensors, one current sensor, one voltage sensor, all sensors being externally connectable, and an enclosure in which a thermal energy calculation IC board, an electrical power calculation IC board, and a programmable logic controller are arranged. The enclosure has a front side to which a man-machine interface panel that displays measurement readings and provides function-related operations is mounted. The enclosure has a back side to which a socket-carrying panel that is connectable to cables of the sensors is mounted. Readings of flowrate, temperature, current, and voltage are transmitted to the programmable logic controller in which software is executed to compile and integrate these signals to be further transmitted to a computer for subsequent analysis and monitoring. Test of a water chiller is made simple and cost, man power, and working hours are saved.