The invention relates to an image coding apparatus which can improve the picture quality of an image. A quantization scale arithmetic operation section 43 calculates a coefficient of a quantization index based on a variance of values of a motion vector residual outputted from a motion vector residual variable buffer section 72 and an activity outputted from an activity buffer section 73. The quantization scale arithmetic operation section 43 calculates a quantization scale based on the coefficient of the quantization index calculated thereby and the quantization index outputted from the quantization index arithmetic operation section 42. The present invention can be applied to an image coding apparatus of the MPEG system.