A moving image coding device (10a) comprises a level analyzer (100a) that determines the maximum number of codable on-screen pixels (Nfpx) based on a level identifier (Lst) indicating a user-specified coding level and the maximum number of stored pixels (Nspx) that can be stored in the picture memory of a decoding device. Based on the maximum number of on-screen pixels (Nfpx) and an input image size (number of vertical pixels (Nhpx) and number of horizontal pixels (Nwpx)), the moving image coding device (10a) determines if an input image can be coded and, at the same time, calculates the maximum number of reference pictures (Nrpn) that is the number of reference candidate pictures that can be referenced during inter-picture predictive coding. A decoding device, which receives a code string from such a moving picture coding device (10a), can always decode the code string properly and can perform inter-picture predictive decoding corresponding to inter-picture predictive coding on the coding side. As a result, it is possible to design the memory area of a coding device and a decoding device compatible with a coding method that does not limit the capacity of the memory area.