Oxygen uptake and release of (Li,Mn) ferrite [LMF; (Li0.60Mn1.20Fe1.20)(1-delta)O-4; delta = 0.007 to 0.033] was investigated concerning the relations between redox reactions of ferrite and cation migration. Mossbauer spectroscopy and X-ray diffractometry showed that some of the Li+ and Fe3+ ions migrated from the A sites to the B sites of the spinel-type structure and Mn4+ ions migrated from the B sites to the A sites during oxygen uptake at 573 K. The cation-deficient LMF formed by the oxygen uptake released oxygen molecules in He gas only at 660 K. The cation migration during the oxygen release was in the opposite direction of the movement during oxygen uptake at 573 K.