A picture coding apparatus contains a rate control unit 100, an image buffer 200, an orthogonal transformation unit 300, a quantizing unit 400, a variable length coding unit 500, a motion predicting unit 600, a coding unit 700, and an output buffer 800. The rate control unit 100 allocates a target code amount to each of pictures, and transfers a quantizing value 100a which is determined by a code amount to the quantizing unit 400. This target code amount is calculated by adding a reference target code amount to a correction value. The correction value is calculated based on a difference between a predetermined target value and an actual value of a remaining coding picture amount of the output buffer 800.