The present invention provides a manufacturing method for a magnetic disk-use glass substrate which can sufficiently reduce substrate surface defects by suppressing the remains of washing off abrasive grains. In the present invention, a circular plate-shaped substrate is sandwiched using a pair of platens for which polishing pads have been deployed on the surface thereof, a polishing fluid which includes colloidal silica as abrasive grains is supplied to the polishing surfaces, and the main surfaces of the circular plate-shaped substrate are polished. The polishing fluid includes, as an additive, the following substance which comprises a specified amide group or urea group. R[1]-NH-CO-R[2] In the formula, R[1] represents an alkyl group or a hydrogen atom, R[2] represents an alkyl group or -NH-R[3], and R[3] represents an alkyl group.