To provide an apparatus for treating a VOC gas which can evenly and efficiently perform the mixing of a carrier.

In the apparatus for treating the VOC gas which collects an exhaust gas (a) containing VOC, introduces it to an organism-treating vessel 1 filled with a carrier with deposited microorganisms to be biologically decomposed, and an agitator agitating the carrier with an agitating blade 12 extending in a crossing direction from a rotary shaft 11 and agitating rods 13 extending in a crossing direction from the agitating blade 12, the agitating rods 13 are rotatably installed along the agitating blade 12 and a cum mechanism is installed which moves the agitating rods 13 reciprocally.