An image coding apparatus is mainly characterized by (i) dividing each of fields into an I-slice and P-slices, and determining the position of the I-slice in each of a predetermined number of first fields such that a current I-slice is sequentially shifted from the first end of a starting first field to the second end of an ending first field and such that a similar shift is repeated for each predetermined number of first fields, when a current field is a first field, and further (ii) determining, when the current field is the first field, that each P-slice located closer to the first end than a corresponding I-slice can refer to only a first field coded immediately before, and determining, when the current field is the second field, that at least one second field in the predetermined number of fields can refer to only a first field coded immediately before.