An electroplating apparatus is provided that minimizes unplated regions when an alloy plating layer is provided on the surface of a thread on a steel pipe. An electroplating apparatus (10) includes an electrode (1), sealing members (2, 3), and a plating-solution supply unit (4). The electrode (1) faces the thread (Tm). The sealing member (2) is positioned within the steel pipe (P1). The sealing member (3) is attached to the end portion of the steel pipe (P1) and, together with the sealing member (2), forms a receiving space (8). The plating-solution supply unit (4) includes a plurality of nozzles (42). The nozzles (42) are positioned within the receiving space (8) and adjacent one end of the thread (Tm) and arranged around the pipe axis of the steel pipe (P1). The plating-solution supply unit (4) injects a plating solution between the thread (Tm) and electrode (1) through the nozzles (42). The direction in which plating solution is injected from the nozzles (42) is inclined at an angle larger than 20 degrees and smaller than 90 degrees toward the thread (Tm) relative to a plane perpendicular to the pipe axis.