The high-speed and high-quality reception operation of a transimpedance amplifier of an optical communication module and a router including the same can be achieved. A preamplifier performs current/voltage conversion with respect to intersymbol interference due to bandwidth shortage of a laser diode. A threshold control circuit which generates positive and negative threshold voltages with respect to a center potential of an output signal, latch circuits, and a selector circuit are provided to the output of the preamplifier. An NRZ signal is received as a duobinary signal based on the sign determination result of the previous bit. The determination error rate of the latch circuits can thus be improved.