Kerr rotation spectrum in ferromagnetic CrBr 3 is discussed on the electronic states of a (CrBr 6 ) 3 - octahedral cluster calculated by a USCF-X α SW method, and on the signs of spin-orbit constants in the charge transfer (CT) states. The observed positive peak at 23500 cm - l and the negative one at 26500 cm - 1 are assigned to the t 1 u n -> e g * and t 2 u n -> e g * CT transitions, respectively, contrary to the previous study by Jung. By the present assignment, the observed Kerr rotation spectrum is reproduced quite well.