When the discharge current is supplied with a first pulse width T1, switching elements (10) are controlled by control means (11) so that a predetermined amount of electrode material is supplied, a first peak value Ip1 is adjusted to a predetermined one, the electrode material is released, and an electrode component (15a) is made to adhere to a work (2). When the discharge current is supplied with a second pulse width T2, a second peak value Ip2 is so adjusted that the release of the electrode material can be controlled and the electrode component (15a) adhering to the work (2) can be melted, the electrode component (15a) is thus melted, and a hard coating made from the melted electrode component (15b) is formed on the work (2). The hard coating is a good coating containing crystallite particles.