A coding method includes: defining an access unit; and coding each of the pictures included in the access unit, for each access unit. The defining includes: determining a unit of coding for determining whether the pictures included in the access unit are to be uniformly coded on a per-field basis or on a per-frame basis; and determining a field type for determining whether the pictures are to be uniformly coded as top fields or bottom fields when it is determined that the pictures included in the access unit are to be coded on a per-field basis. In the coding, each of the pictures is coded for each access unit in a format determined in the determining of a unit of coding and in the determining of a field type.