Method and apparatus for adjusting an image formation speed with respect to printing data transferred from a digital office device. To that end, an internal temperature and an operation environment of the digital office device are measured. The measured internal temperature and the operation environment are used to calculate a first threshold output sheet number. When the sheet number of the image formation with respect to the transferred printing data exceeds the first threshold output sheet number, the operation environment is used to adjust the image formation speed with respect to the printing data.