Purification method and production method of cyclic peptide

A purification method of a cyclic peptide,

• the purification method comprising the following separation step (i) or (ii):
• (i) separating a cyclic peptide that is a purification target from a mixture containing the cyclic peptide that is a purification target as a composite with a metal atom or a metal ion, or
• (ii) separating a cyclic peptide that is a purification target or a peptide that is an impurity from a mixture containing the cyclic peptide that is a purification target and the peptide that is an impurity as a composite with a metal atom or a metal ion, wherein
• the metal atom is at least one selected from the group consisting of an alkali metal atom, an alkaline earth metal atom, a transition metal atom, a poor metal atom, and a rare earth metal atom, and
• the metal ion is at least one selected from the group consisting of an alkali metal ion, an alkaline earth metal ion, a transition metal ion, a poor metal ion, and a rare earth metal ion.