A three state emitter coupled logic circuit has a logic circuit responsive to an input logic signal and a three state control signal, a difference circuit formed by two series combination of resistors and bipolar transistors coupled in parallel as well as a constant current source coupled between the difference circuit and a constant source, and an emitter follower circuit coupled to an intermediate node between one of the resistors and one of the bipolar transistors for producing an output signal, and a bypassing circuit is provided in parallel to the constant current source for increasing the amount of current passing through the difference circuit in the presence of the three state control signal of the active level, so that the voltage level at the intermediate node is varied out of the usual voltage range for the logic function mode, thereby the three state emitter coupled logic circuit being established in the high impedance state.