A manufacturing method for a glass substrate having a hole with a depth of d (μm) or more includes irradiating the glass substrate with a laser beam emitted from a CO2 laser oscillator for an irradiation time t (μsec), to form a hole in the glass substrate. The laser beam is delivered to the glass substrate after being condensed at a focusing lens. A power density Pd (W/cm2), defined by Pd=P0/S where P0 and S are a power and a beam cross-sectional area of the laser beam just prior to entering the focusing lens, respectively, is 600 W/cm2 or less. The irradiation time t (μsec) satisfies t≥10×d/(Pd)1/2.