TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compound: The 90 % cumulative mass-particle size distribution diameter (D9O) of (I) is less than or equal to 2.2 microns. The distribution constant n of (I) according to the Rosin-Rammler formula as given in the specification is 1.7 - 3.5. The BET specific surface area is alpha (m2/g) and the mass decrement when the powder is ignited in an electric furnace kept at 900 degrees C for 1 hour (loss on ignition) is X (mass%) which is represented by a formula as given in the specification. The Fe, A1 and S contents each is less than or equal to 10 ppm by mass in (I); and the content of Cl in the powder body of (I) is less than or equal to 50 mass% of the loss on ignition.Preferred Method: The amount of water vapor contacted is 2 - 30 mol per mol of (A1). (A1) and the oxidative gas supplied to the reaction tube are preheated at a temperature of 600 degrees C - less than 1,1100 degrees C. In the contacting step: the water vapor and the powder body are counter-currently contacted by introducing the water vapor into the heating furnace at a ratio of 1 - 60 (preferably 1 - 50) mass% based on the titanium dioxide powder; the titanium dioxide is heated at 150 - 500 degrees C; the residence time of the powder in the heating furnace is 0.5 - less than 3 hours.Preferred Component: The oxidative gas is water vapor. EXAMPLE - Titanium tetrachloride (5 kg/hour) diluted with nitrogen gas (25 Nm3/hour) was preheated to 1100 degrees C and introduced into a reaction tube. Similarly, water vapor (55 Nm3/hour) was heated to 1100 degrees C and introduced into the reaction tube and through a reaction with the titanium tetrachloride gas, fine titanium dioxide particles were obtained. These fine particles were collected by a polytetrafluoroethylene-made bag filter and then introduced into an external heating-type rotary kiln. The external heating-type rotary kiln had a structure that a stir-up blade for stirring the powder body was provided in the inside. The rotary kiln was set to a temperature of 400 degrees C, and the residence time of the powder body was adjusted to 1 hour by controlling the length of high-temperature zone, the rotating speed and the angle at which the kiln was installed. Separately, water vapor in an amount of 30 mass% based on the mass of titanium dioxide passing through the kiln was introduced from the outlet for the powder body in the rotary kiln, thereby counter-currently contacting the powder body and the water vapor. Incidentally, the water vapor introduced was previously heated to 120 - 200 degrees C. In the thus-obtained powder body, the BET specific surface area was 158 m2/g, the entire chlorine content was 13,000 ppm by mass, Fe was 2 ppm, A1 was less than or equal to 2 ppm , and S was less than or equal to 2 ppm. The 90 % cumulative mass-particle size distribution diameter D90 was 0.8 microns. Also, 2 g of the powder was spread in a 10 cm-diameter glass-made Petri dish to a uniform thickness and left standing in an environment at 20degreesC and a relative humidity of 80 % for 5 hours, and then the rate of change of mass based on the mass before standing was measured and found to be 3.6 mass%. The mass decrement when the powder was ignited in an electric furnace kept at 900 degrees C for 1 hour, that was, the loss on ignition was 6.5 mass%. The BET specific surface area of the sample after the measurement of loss on ignition was 3.5 m2/g; and the distribution constant n was 3.2.