A method for manufacturing a magnetic disk glass substrate including a chemical strengthening step is provided. In the method, chemical strengthening treatment is sufficiently performed over the entire main surfaces of a glass substrate. Consequently, the resulting magnetic disk glass substrate can provide a magnetic disk allowing the magnetic head to have a low flying height and achieving high-density information recording, and particularly a magnetic desk suitably used in small hard disk drives for portable information apparatuses. In the chemical strengthening step, a chemical strengthening agent is brought into contact with a glass substrate to perform ion exchange by allowing the chemical strengthening agent to flow with respect to the glass substrate, or by moving the glass substrate with respect to the chemical strengthening agent.