1. A moving image encoding apparatus that encodes each picture by dividing the picture into a plurality of slices, the moving image encoding apparatus comprising: slice division structure control means for determining a slice division structure indicating a division position for dividing the picture into a plurality of slices; pre-stage processing means for performing pre-stage processing that can yield different processing results for different slice division structures, the pre-stage processing being processing for a pre-stage portion for encoding the picture; and post-stage processing means for performing post-stage processing based on the processing result of the pre-stage processing means to obtain an encoding result, the post-stage processing being processing for a post-stage portion for the encoding, wherein the pre-stage processing means performs the pre-stage processing for each of a plurality of slice division structures that can be determined by the slice division structure control means, and obtains processing results for each of the plurality of slice division structures, and the post-stage processing means selects, from among processing results for each of the plurality of slice division structures obtained by the pre-stage processing means, a processing result matching a slice division structure determined by the slice division structure control means, and performs the post-stage processing based on the selected processing result.