A double-balanced mixer, including a coupling transformer, a first diode cascade circuit, a second diode cascade circuit, and a first set of coils, is provided. The coupling transformer receives a first input signal and generates at least one set of signals with opposite voltage phases. The first diode cascade circuit is coupled to the coupling transformer, and generates a first node voltage according to a first set of bias voltages. The second diode cascade circuit is coupled to the coupling transformer, and generates a second node voltage according to a second set of bias voltages. The first set of coils is coupled to the first and second diode cascade circuits, receives the first and second node voltages and a second input signal, and generates an output signal. The first node voltage is equal to the second node voltage.