The present invention addresses the problem of obtaining an anti repulsive guidance molecule a (RGMa) antibody which has a high binding activity and few side effects and can be used as a medicine for preventing treating or preventing the relapse of neurological or immunological diseases. Said problem is solved by providing an isolated RGMa binding protein which does not inhibit binding between RGMa and neogenin but neutralizes the neuritis growth inhibiting activity of RGMa and preferably by providing an anti RGMa antibody which has a complementarity determining region having an amino acid sequence of SEQ ID NOS: 30 35 or SEQ ID NOS: 36 40 in the sequence listing and SFG.
