The present invention includes: plural common terminals; plural water level measurement terminals that are arranged at a certain interval along a longitudinal direction; a water level measurement control unit that measures the water level of a measurement subject by letting an electric current flow to the plural common terminals, then reading the state information of an electric current flowing to the plural water level measurement terminals; and an LED unit that reads and displays the water level measurement results through plural LEDs. The water level measurement system according to the invention comprises: the above-mentioned water level display device; a main control module that controls the water level display device to read the water level measurement results from the water level display device and display the water level measurement results in numerical form or on a scale; a power supply module that supplies power to the water level display device under the control of the main control module; and a display module that displays the water level measurement results according to control of the main control module.