The invention relates to a device and a method for treating VOCs (volatile organic compounds), and the method comprises the following steps: pressurizing VOCs gas, feeding the VOCs gas into a catalytic cracking riser reactor, and feeding the gas obtained by reaction into a separation and purification system of a catalytic cracking device along with catalytic cracking reaction oil gas. According to the present invention, an existing catalytic cracking unit riser reactor in a refinery plant and a product separation and purification system thereof are adopted, the reaction recovery method is adopted, the VOCs gas is simply and efficiently recovered and utilized, a VOCs gas treatment device does not need to be additionally arranged, and the disadvantages of high investment, heat waste, serious secondary pollution and the like of a traditional combustion method are avoided; and according to the method, sulfur, nitrogen and other impurities in the VOCs gas can be effectively removed, and meanwhile, the pre-lifting steam consumption of a riser reactor of a catalytic cracking device can be reduced, so that the cooling water consumption of a fractionating tower in the oil gas fractionation process and the amount of sulfur-containing ammonia sewage discharged by the device are reduced, and the energy consumption and the operation cost of the device are reduced.