It is stipulated by the Ministry of Welfare to use carbon blacks of channel type which are free from Benzo[a]pyrene (BaP) as materials for cosmetics. But BaP is absorbed by carbon blacks so securely that it is not extracted easily with usual organic solvents. This paper describes simple determination method of BaP in carbon blacks. The 100 mg of carbon black was extracted for 5 minutes with hot 1-chloronaphthalene : monochlorobenzene (1 : 1) with shaking. BaP in the filtered solution was determined fluorometrically at 409±3 nm (Ex. 390 nm) by the use of baseline method. Since recovery of BaP added to the carbon blacks was still low because of BaP absorption and coexistent substances, the standard addition method was used to increase the accuracy. The possible intervention of 11 polycyclic aromatic hydrocarbons (PAH) in this method was studied, which may be coexistent in carbon blacks. As the result it was found that benzo[g, h, i]perylene and benzo[k]fluoranthene were added to the BaP figure if in coexistence, while all the other PAH did not affect the determination. When these two hydrocarbons coexisted, a figure could be drawn according to the ratio of the peaks height of their fluorescence spectrum patterns, which could be used to adjust the measurements and obtain nearly precise BaP values. The BaP content of carbon blacks specimens ranged from ND-5.6 ppm for both types of carbon blacks. It was worth mentioning that 209 ppm of BaP was detected in the soot from burned kerosene.