The etching step includes primary laser irradiation and a secondary laser irradiation. The pattern 50 is formed in the precoat 60 through the primary laser irradiation. Then, an uneven portion is formed by the secondary laser irradiation on the upper surface of the metal substrate 10 exposed by the primary laser irradiation. Preferably, the electric power (Watt) at the time of secondary laser irradiation is lower than the electric power at the time of primary laser irradiation. More specifically, the electric power at the time of secondary laser irradiation may be set to become ? or less of the electric power at the time of primary laser irradiation. In addition, the electric power at the time of primary laser irradiation may be set to 40% of the electric power of a laser irradiation device. The electric power at the time of secondary laser irradiation may be set to 10% of the electric power of the laser irradiation device.

By performing the laser irradiation at two levels in this way, it is possible to further enhance the accuracy of the pattern 50.

As shown in FIG. 8, the maximum depth of the groove of the uneven portion formed when the electric power of the laser irradiation device is 1.5 W is 2.36 μm and the maximum width of the groove is 13.35 μm.

As shown in FIG. 9, the maximum depth of the groove of the uneven portion formed when the electric power of the laser irradiation device is 7.5 W is 8.71 μm and the maximum width of the groove is 19.11 μm.

As shown in FIG. 10, the maximum depth of the groove of the uneven portion formed when the electric power of the laser irradiation device is 15 W is 8.85 μm and the maximum width of the groove is 25.95 μm.