Abstract: A problem to be solved is to enhance the charge and discharge characteristics and rate characteristics of a B-type titanium oxide (TiO2(B)) powder by a simple treatment and to provide a B-type titanium oxide powder that can be suitably used as a negative electrode material for a lithium ion battery. A B-type titanium oxide powder is allowed to undergo a reaction under a fluorine-containing gas atmosphere at 0° C. to 200° C. for 1 minute to 10 days to obtain a surface-fluorinated B-type titanium oxide powder. It is preferred that the fluorination treatment is performed at 0.01 atm to 2 atm. It is preferred that a gas containing a fluorine compound selected from a fluorine (F2) gas, a nitrogen trifluoride (NF3) gas, a perfluorotrimethylamine (N(CF3)3) gas, a chlorine trifluoride (ClF3) gas and the like is used as the fluorine-containing gas.