There is provided an image information process apparatus to be applied to a display for displaying bit image display data for each pixel, for enabling the display to display continuous tones in an error diffusion manner based on P bit image data, P being larger than L. This apparatus includes a plurality of adding circuits to which a plurality of P bit image data are concurrently supplied. A predetermined lower bit of an added result at respective adding circuits is used as error data supplied to the next adjacent adding circuit. An error data holding circuit holds a predetermined lower bit of an output from an adding circuit corresponding to the last column pixel in image data supplied. It then supplies the lower bit held to an adding circuit corresponding to the top front column pixel of the image data supplied. With this arrangement, a display which is capable of displaying images based on digital data of a limited number of bits displays in a pseudo manner continuous tones expressed using a higher number of bits than the limited number. In addition, performance and processing speed of image information processing are improved.