A breast cancer pathological image diagnosis support system for supporting a diagnosis of breast cancer based on a pathological image is provided. The breast cancer pathological image diagnosis support system includes an image obtaining unit which obtains an HE-stained image and an IHC image as pathological images to be diagnosed; an information obtaining unit which obtains information of a tumor area in the HE-stained image; a matching unit which calculates a matching position of the HE-stained image and the IHC image obtained by the image obtaining unit; a specifying unit which specifies a tumor area in the IHC image based on the information of the tumor area in the HE-stained image obtained by the information obtaining unit and information of the matching position calculated by the matching unit; and a calculating unit which calculates a staining positive cell content rate in the tumor area based on information of the tumor area in the IHC image specified by the specifying unit.