1. An image coding method comprising: setting positions and sizes of designated slices of an image, the designated slices including at least two independent rectangular slice of at least two respective regions that partially overlap and at least one slice of a region that surrounds at least one of the at least two partially overlapping regions; coding, using at least one processing device, respective information on positions and sizes of the designated slices to a picture header; and coding an image in units of slices by referring to the picture header.