A splitter circuit improves isolation between output ports. The splitter circuit comprises input port 1, output port 2, output port 3, FET 6, FET 11 and an impedance circuit. FET 6 is provided between input port 1 and output port 2 and adapted to amplify a signal at input port 1 to output an amplified signal to output port 2. FET 11 is provided between the input port 1 and the output port 3 and adapted to amplify a signal at input port 1 to output an amplified signal to the output port 3. The impedance circuit couples the output ports 2 and 3, and includes a first series circuit including inductor 15 and diode 17, series connected to each other, a second series circuit including inductor 16 and diode 18, series connected to each other, and resistor 19. The first series circuit has one end connected to output port 2 and the second series circuit has one end connected to output port 3. The resistor is connected between the other ends of the first and second series circuits and the ground. Diodes 17, 18 are connected so that current will flow in forward direction when voltage of a power supply is applied to FETs 6 and 11 (FIG. 1).