Abstract: The present invention provides a two-stage centrifugal compressor. The compressor of this invention has a simplified refrigerant passage structure and effectively cools its electric motor in addition to bearing parts using an existing refrigeration cycle without having another external cooling unit. This compressor thus reduces a consumption of electric power, and improves the operational performance and operational efficiency of a refrigeration system. In the two-stage centrifugal compressor of this invention, a plurality of internal fluid passages is regularly formed on the internal surface of the upper and lower end portions of an external housing so as to allow first and second compression parts to communicate with each other through the interior space of the external housing.