An image processing apparatus comprising an acquiring unit configured to acquire an encoding target block having a plurality of groups each including a predetermined number of pixels, a deciding unit configured to decide, for each group, a quantization parameter used to quantize image data of the group and an encoding scheme so that a code length of the encoding target block does not exceed a predetermined value corresponding to a target code amount of the encoding target block, and an encoding unit configured to generate encoded data by encoding image data of the encoding target block in accordance with the quantization parameters and the encoding schemes decided for the respective groups by the deciding unit.