A substrate manufacturing method, comprising: - a first step of disposing a condenser for condensing a laser beam in a non-contact manner on an irradiated surface of a single crystal member of magnesium oxide to be irradiated; the method being characterised by the following steps: - a second step of irradiating a laser beam to a surface of the single crystal member and condensing the laser beam into an inner portion of the single crystal member under designated irradiation conditions using the condenser, and at the same time, two-dimensionally moving the condenser and the single crystal member relative to each other and sequentially forming processing mark lines in parallel; and - a third step of irradiating a laser beam to a surface of the single crystal member and condensing the laser beam into an inner portion of the single crystal member under designated irradiation conditions using the condenser, and at the same time, two-dimensionally moving the condenser and the single crystal member relative to each other and forming new processing mark lines between the adjacent processing mark lines formed by the irradiation in the second step, to allow planar separation, wherein in the second step, a reflection layer that reflects the irradiated laser beam in the third step is formed by the processed layer formed around the processing marks, such that the reflection layers of the processing marks in adjacent irradiation lines and adjacent to each other in the scanning direction overlap each other, wherein in the third step, the laser beam is reflected on the reflection layer, the reflection layer is formed at a lower separation plane, and large-diameter holes are formed on an upper separation plane opposite the reflection layer due to the reflection of the laser beam from the reflection layer. - a first step of disposing a condenser for condensing a laser beam in a non-contact manner on an irradiated surface of a single crystal member of magnesium oxide to be irradiated; - a second step of irradiating a laser beam to a surface of the single crystal member and condensing the laser beam into an inner portion of the single crystal member under designated irradiation conditions using the condenser, and at the same time, two-dimensionally moving the condenser and the single crystal member relative to each other and sequentially forming processing mark lines in parallel; and - a third step of irradiating a laser beam to a surface of the single crystal member and condensing the laser beam into an inner portion of the single crystal member under designated irradiation conditions using the condenser, and at the same time, two-dimensionally moving the condenser and the single crystal member relative to each other and forming new processing mark lines between the adjacent processing mark lines formed by the irradiation in the second step, to allow planar separation, wherein in the second step, a reflection layer that reflects the irradiated laser beam in the third step is formed by the processed layer formed around the processing marks, such that the reflection layers of the processing marks in adjacent irradiation lines and adjacent to each other in the scanning direction overlap each other, wherein in the third step, the laser beam is reflected on the reflection layer, the reflection layer is formed at a lower separation plane, and large-diameter holes are formed on an upper separation plane opposite the reflection layer due to the reflection of the laser beam from the reflection layer. wherein in the second step, a reflection layer that reflects the irradiated laser beam in the third step is formed by the processed layer formed around the processing marks, such that the reflection layers of the processing marks in adjacent irradiation lines and adjacent to each other in the scanning direction overlap each other, wherein in the third step, the laser beam is reflected on the reflection layer, the reflection layer is formed at a lower separation plane, and large-diameter holes are formed on an upper separation plane opposite the reflection layer due to the reflection of the laser beam from the reflection layer.