A slice division structure control unit (430) determines a slice division structure indicating a division position for dividing each picture into multiple slices. A pre-stage processing unit (410) performs pre-stage processing of encoding for each of multiple slice division structures that can be determined by the slice division structure control unit (430), and obtains processing results for each of the multiple slice division structures. A post-stage processing unit (420) selects, from among the processing results for each of the multiple slice division structures obtained by the pre-stage processing unit (410), a processing result matching a slice division structure (S) determined by the slice division structure control unit (430), and performs post-stage processing for encoding the picture based on the selected processing result. With this configuration, deterioration in image quality and efficiency can be avoided even when the slice division structure is dynamically changed during encoding of a moving image.