A hierarchical coding apparatus comprising first and second compressive coding units for subjecting high- and low-resolution digital image signals to hierarchical coding to generate high- and low-resolution coded data, and a resolution conversion circuit for subjecting a portion of low-resolution decoded image signal obtained by decoding the low-resolution coded data to resolution conversion, wherein only the resolution converted image signal is used as a reference signal for a low resolution side in coding the high-resolution digital image signal, thereby making the reduction of compression efficiency of image data, which is transmitted or stored, less, and simplifying the configuration of the hierarchical coding apparatus.