An image processing device capable of processing images containing poorly contrasted letters and/or bold letters in addition to well contrasted letters and pictures such that both resolutions of letters and tones of pictures can be preserved. The device may includes a circuit to distinguish two level images from non two level images according to image concentration related quantity, and a circuit to distinguish picture images out of non two level images according to another image concentration related quantity. The device may include a circuit to distinguish letters from pictures according to the maximum and the minimum values of the image concentration related quantity. The device may includes a circuit to distinguish letters from pictures according to the maximum and the minimum values of changes in the image concentration related quantity. The device may include a circuit to distinguish letters from pictures according to the square sum average of differences in the image concentration related quantity between neighboring picture elements.