A device and a method for post-processing of computed tomography (CT), which are adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver, are provided. The method includes: obtaining the identification image including a liver region and a non-liver region and a Hounsfield unit (HU) value of each pixel corresponding the identification image, wherein the liver region includes an FNH candidate region; calculating an average HU of the liver region; adjusting an HU value of the non-liver region to the average HU value of the liver region with respect to the identification image to generate a processed identification image; and updating the FNH candidate region according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate region.