A method of manufacturing an electrode composite for forming an electrode of a spark plug, the electrode composite being formed by laser-welding a first electrode member and a second electrode member together, the method comprising: a first electrode member holding step of holding the first electrode member by a chuck of a chuck unit; a second electrode member supply step of supplying the second electrode member such that an end surface of the second electrode member comes into contact with an end surface of the first electrode member; and a laser welding step of welding outer circumferential edges of the end surfaces (13, 23) through which the first electrode member and the second electrode member are in contact with each other; the method being characterized by further comprising: an eccentric error detection step coming after the first electrode member holding step and before the second electrode member supply step and adapted to detect an eccentric error between a position of an actual center axis of the first electrode member and a shaft of a base rotatably supporting the chuck of the chuck unit; and a center axis position correction step of correcting the position of the actual center axis of the first electrode member when the eccentric error detected in the eccentric error detection step falls outside a tolerance range subsequent to the eccentric error detection step, so as to align the actual center axis of the first electrode member with an axis of the shaft of the base. a first electrode member holding step of holding the first electrode member by a chuck of a chuck unit; a second electrode member supply step of supplying the second electrode member such that an end surface of the second electrode member comes into contact with an end surface of the first electrode member; and a laser welding step of welding outer circumferential edges of the end surfaces (13, 23) through which the first electrode member and the second electrode member are in contact with each other; the method being characterized by further comprising: an eccentric error detection step coming after the first electrode member holding step and before the second electrode member supply step and adapted to detect an eccentric error between a position of an actual center axis of the first electrode member and a shaft of a base rotatably supporting the chuck of the chuck unit; and a center axis position correction step of correcting the position of the actual center axis of the first electrode member when the eccentric error detected in the eccentric error detection step falls outside a tolerance range subsequent to the eccentric error detection step, so as to align the actual center axis of the first electrode member with an axis of the shaft of the base. an eccentric error detection step coming after the first electrode member holding step and before the second electrode member supply step and adapted to detect an eccentric error between a position of an actual center axis of the first electrode member and a shaft of a base rotatably supporting the chuck of the chuck unit; and a center axis position correction step of correcting the position of the actual center axis of the first electrode member when the eccentric error detected in the eccentric error detection step falls outside a tolerance range subsequent to the eccentric error detection step, so as to align the actual center axis of the first electrode member with an axis of the shaft of the base.