To provide a follower machining method of a roller gear indexer capable of dispensing with the correction of the setting of an output shaft on a machining device in drilling the mounting holes of a follower wheel part, and drilling the mounting holes with high accuracy in the indexing angles among a plurality of mounting holes.

An output shaft 5 is rotated in a held state between a chuck 2 of an index disc 3 and a center 4, the eccentric amount (e) and the eccentric direction on the mounting hole drilling position H are measured on the basis of the run-out of the central axis of the bearing support parts 5B, 5C to the central axis X of the rotation, an angle θ of the eccentric direction to the central axis of a drilling tool T on every index position of the follower wheel part 5A by the index disc is calculated, and drilling is executed on a position where the drilling tool is moved in prallel from a position where an extension line of the central axis of the drilling tool intersects with the rotation central axis X, to a position where the extension line intersects with the central axis of the bearing support part by esinθ.