Disclosed is an apparatus and method for decomposing an ultra-low concentration of volatile organic compounds, which may effectively remove ultra-low concentration of volatile organic compounds by a batch process for separating ultra-low concentration of volatile organic compounds present in an indoor air or the like and oxidizing the corresponding volatile organic compounds at a low temperature. The apparatus includes a contaminated air source for supplying a contaminated air containing volatile organic compounds, two or more absorption/desorption modules connected to the contaminated air source in parallel, a heating device provided at a circumference of each absorption/desorption module, and an oxidation decomposing catalyst device for reacting volatile organic compounds discharging from the absorption/desorption modules with oxygen atoms (O*) in an activated state so that the volatile organic compounds are oxidized and decomposed, wherein each absorption/desorption module alternately performs an absorption process and a desorption process.