An image coding device for reducing flicker noise in moving image coding based on Motion JPEG-2000, which applies wavelet transform to an input image, quantizes the wavelet transform coefficients, and replaces quantization coefficients of adjacent frames in accordance with a predetermined judgment condition. The device spreads the finally output quantization coefficients into bit-planes from the MSB to LSB, generates coding passes in each bit-plane, performs arithmetic coding in the coding passes, controls the code quantity to a target code quantity from the generated arithmetic codes, and generates a packet of the image data by attaching a header to the arithmetic codes. The quantization coefficients are replaced based on a difference of absolute values of the quantization coefficients at the same sub-band in the adjacent frames. By further adding the wavelet transform coefficients, erroneous detection in the substitution processing can be decreased and the flicker noise can be suppressed effectively. Also, an image coding method for the same.