A category setting part sets a type of a decoded image based on characteristics of the decoded image which are fineness of the decoded image and an intensity of movement of the decoded image. A code amount setting part sets a target code amount of an output image based on the type of the decoded image. A quantization step value setting part sets a quantization step value of the output image based on the target code amount of the output image. A transcoder can set the target code amount of the output image depending on fineness of the decoded image. The transcoder can distribute the target code amount of the output image to a reference image and a predicted image depending on the intensity of movement of the decoded image.