PURPOSE: To decide the amount of codes to be allocated to an area in an image corresponding to characters inside the image by dividing this area so as to suppress the fluctuation of a quantizing scale in the image and to uniform the picture quality inside the image by controlling the amount of generated codes so as to be the amount of codes allocated to respective images.

CONSTITUTION: An in-slice feature amount calculation part 15 calculates an in-slice feature amount from the quantizing scale and the amount of generated codes for the unit of a slice, and an in-image feature amount calculation part 17 calculates an in-image feature amount from the in-slice feature amount. Corresponding to these feature amounts, a slice allocating code amount calculation part 17 and an in-image allocating code amount calculation part 20 calculate an in-image allocating code amount and an in-slice allocating code amount. A subtracter 21 generates a remaining code amount by subtracting a slice generating code amount from the output of the slice allocating code amount calculation part 18. An adder 24 adds a code amount, which is added to the remaining code amount by an adder 22 and a memory 23, with the output of the in-image allocating code amount calculation part 20.