PURPOSE: To keep the reproducibility of a fine line by a digital exposing means excellent, regardless of the size of the dot diameter, etc., of the digital exposing means, in an image forming device provided with an analog and the digital exposing means.

CONSTITUTION: When the dot diameter, etc., of the digital exposing means L1 is changed, and the ratio of the output interval of a dot to its diameter exceeds a fixed value, a detecting means 60 detects the fact. When the digital exposing means L1 forms a latent image, a control means 61 changes at least either of a latent image condition or a developing condition based on a signal from a detecting means 60 to make developing contrast wide.