An equalizer for compensating transmission losses of electronic communication signals includes a circuit board and a compensation module. The compensation module includes a pair of input pins, a pair of output pins, first and second resistors, first and second vias, and a pair of micro-strips. When a signal transmitted by the circuit board is received by the input pins, a first part of the signal is directly outputted from the output pins, a second part of the signal is reflected by the first resistor and transmitted back to the output pins to be outputted, and a third part of the signal is reflected by the second resistor and transmitted back to the output pins to be outputted, such that the output of the equalizer applies two stages of compensation.