PURPOSE: To set slope control easily by extracting the characteristics value of a photographic picture, storing the characteristics value and a corresponding photographic printing exposure time in a pair, and performing calculation for interpolation between data in the pair and printing on the stored condition.

CONSTITUTION: A picture on a photographic film such as a negative is converted into an electric signal by a photoelectric converting means 1 and a characteristics value extracting means 2 extracts the predetermined characteristics value. An exposure control part 3 controls printing exposure to photosensitive paper, etc., on the basis of the output of the means 2. Then, the output of the means 2 and the output of the control part 3 are stored in a data storage part 5 through a data input part 4. When initially standard data on a pair of a characteristics value and an exposure time are inputted to the storage part 5 and a new negative is set, exposure control is performed on the basis of an output characteristics value and the characteristics value corresponding to the exposure time is inputted to the storage part 5. An interpolation arithmetic part 6 performs calculation for interpolation between the data in the pair and performs printing on corrected condition. Thus, the slope control by the negative is facilitated.