We analyzed the head noise in CPP-GMR heads to clarify the effect of shape anisotropy on spin-torque noise through an experiment and calculations. We fabricated two types of CPP-GMR heads with a current-screen layer (a nano-oxide layer with a confined current path), using two different track widths (50 nm and 90 nm) and the same stripe height (100 nm). The measured and calculated noise of a 50-nm-wide-track head is larger than that of a 90-nm one when the sensing bias voltage is 120 mV and the peak asymmetry is the same. This behavior is explained by considering that the shape anisotropy field enhances the tilt of the magnetization, especially at the edge of the track in the free layer, and that this magnetization configuration increases spin torque. Accordingly, we clarified that spin torque noise is sensitive to a head-internal field such as a shape magnetic anisotropy field, and that controlling the shape anisotropy field is important for reducing the spin-torque noise.