The present invention provides a method for manufacturing a fitting that has a configuration where a fitting plate and a blind nut are integrally formed and also provides a tap tool for use in this method. According to the present invention, performing tap processing to an internal diameter portion to integrally form a portion corresponding to the blind nut, when a tap tool having a protrusion at an end thereof is utilized to be inserted into the bag-like blind hole at a planned part of the blind nut and the tap processing is carried out, the protrusion provided at the end of the tap tool comes into contact with an inner wall at the end of the bag-like blind hole, and a pressed material thereby forms a convex shape on an outer side of the bag-like blind hole.