The noise in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with a current screen layer (CSL) is investigated to clarify the noise generation mechanism. The noise intensity is greatly enhanced in the antiparallel magnetization configuration due to spin torque effects. In addition, the noise intensity increases as the temperature is reduced because thermal spin fluctuations decrease. Furthermore, the noise intensity increases when spins flow to the free layer because the magnetization of the free layer fluctuates easily. These results imply that noise is generated by fluctuations in the magnetization of the free layer caused by spin torque. Moreover, some CPP-GMR devices with a CSL have some peaks in plots of noise intensity against applied magnetic field. These peaks are thought to be related to the current-induced field and magnetization fluctuations at the edge of the device.