A discharging surface preparation method of surface preparing an end face portion of a metallic plate extremely narrow in width by using discharge energy, the discharging surface preparation method comprising: a recess forming step of having a compact formed from at least one of powder of metal, powder of compound of metal, and powder of ceramics, employed as an electrode, generating pulsed discharge between an end surface of the electrode and the end face portion of the metallic plate, in a liquid or gas providing an electric insulation property, for using discharge energy thereof, to attrite the electrode, to form in the end surface of the electrode a recess (41, 49) conforming to a shape of the end face portion of the metallic plate; an auxiliary coat forming step of, under a condition holding a prescribed discharge gap, generating pulsed discharge in a liquid or gas providing an electric insulation property, for using discharge energy thereof, to deposit a material of the electrode or a reactant substance thereof on the metallic plate, to form an auxiliary coat (43, 45, 51, 53); and an end coating step of generating pulsed discharge in a liquid or gas providing an electric insulation property, for using discharge energy thereof, to deposit a material of the electrode or a reactant substance thereof on the top face of the end face portion of the metallic plate, to form a cladding layer (47, 55), characterised in that: in the auxiliary coating step, the metallic plate on a table is moved by an X-axis servo motor and a Y-axis servo motor so that the electrode makes a relative movement in a direction (G1, G1') perpendicular to and approaching a lateral side of the metallic plate, thereby generating the pulsed discharge between an internal side face of the recess (41, 49) of the electrode and the lateral face of the end face portion of the metallic plate to form the auxiliary coat (43, 45, 51, 53) on the lateral face; in the end coating step, the electrode is moved by a Z-axis servo motor to approach a top face of the end face portion of the metallic plate, thereby generating the pulsed discharge between a bottom face of the recess (41, 49) of the electrode and the top face of the end face portion of the metallic plate to form the cladding layer (47, 55) on the top face; and the end coating step follows completion of the auxiliary coat forming step. a recess forming step of having a compact formed from at least one of powder of metal, powder of compound of metal, and powder of ceramics, employed as an electrode, generating pulsed discharge between an end surface of the electrode and the end face portion of the metallic plate, in a liquid or gas providing an electric insulation property, for using discharge energy thereof, to attrite the electrode, to form in the end surface of the electrode a recess (41, 49) conforming to a shape of the end face portion of the metallic plate; an auxiliary coat forming step of, under a condition holding a prescribed discharge gap, generating pulsed discharge in a liquid or gas providing an electric insulation property, for using discharge energy thereof, to deposit a material of the electrode or a reactant substance thereof on the metallic plate, to form an auxiliary coat (43, 45, 51, 53); and an end coating step of generating pulsed discharge in a liquid or gas providing an electric insulation property, for using discharge energy thereof, to deposit a material of the electrode or a reactant substance thereof on the top face of the end face portion of the metallic plate, to form a cladding layer (47, 55), characterised in that: in the auxiliary coating step, the metallic plate on a table is moved by an X-axis servo motor and a Y-axis servo motor so that the electrode makes a relative movement in a direction (G1, G1') perpendicular to and approaching a lateral side of the metallic plate, thereby generating the pulsed discharge between an internal side face of the recess (41, 49) of the electrode and the lateral face of the end face portion of the metallic plate to form the auxiliary coat (43, 45, 51, 53) on the lateral face; in the end coating step, the electrode is moved by a Z-axis servo motor to approach a top face of the end face portion of the metallic plate, thereby generating the pulsed discharge between a bottom face of the recess (41, 49) of the electrode and the top face of the end face portion of the metallic plate to form the cladding layer (47, 55) on the top face; and in the auxiliary coating step, the metallic plate on a table is moved by an X-axis servo motor and a Y-axis servo motor so that the electrode makes a relative movement in a direction (G1, G1') perpendicular to and approaching a lateral side of the metallic plate, thereby generating the pulsed discharge between an internal side face of the recess (41, 49) of the electrode and the lateral face of the end face portion of the metallic plate to form the auxiliary coat (43, 45, 51, 53) on the lateral face; in the end coating step, the electrode is moved by a Z-axis servo motor to approach a top face of the end face portion of the metallic plate, thereby generating the pulsed discharge between a bottom face of the recess (41, 49) of the electrode and the top face of the end face portion of the metallic plate to form the cladding layer (47, 55) on the top face; and