A call routing method in VoIP (Voice over Internet Protocol) capable of performing voice service assuring best voice quality is obtained by predicting voice quality using network parameters that affect the voice quality, and then performing a call routing to a gateway with a maximum MOS (Mean Opinion Score) value out of a gateway group. Also, actively responding to organically changing network environment and providing a best call routing path for the network environment before setting up a call, best voice quality can be provided.