To provide a monitoring apparatus effectively controlling the position of the nozzle introducing the raw material hydrocarbon and monitoring the situation in the furnace.

This method uses an oil furnace to produce carbon black which is constituted from the first reaction zone obtaining high temperature gas by burning a fuel and air for fuel or oxygen containing gas, the second reaction zone sequentially mounted to the first reaction zone introducing the hydrocarbon to form carbon black by carbon black forming reaction, and the third reaction zone quenching the carbon black forming reaction by rapidly cooling the temperature, the inside of the furnace is monitored by at least one fiber scope mounted on the furnace wall facing to the second reaction zone.