A power supply apparatus with image scanning function is provided. The power supply apparatus is installed to a portable electronic device to supply power and scan documents, and it is also able to be handheld independently to scan documents. The power supply apparatus includes a battery pack and a scanning module. The battery pack supplies power to an electronic device electrically connected thereto and supplies power to the scanning module. The scanning module scans an object to be scanned and converts image into image data. Thus, the portable electronic device obtains the image data of the object to be scanned.