An image coding method includes a first flag coding step (S501) of coding a first flag that indicates whether a predetermined extension standard of a predetermined image coding standard is used, a second flag coding step (S503) of coding, when the first flag indicates that the extension standard is used (Yes in S502), a second flag that indicates whether a first scheme is used that is a coding scheme included in the extension standard for coding a difference between adjacent-to-each-other samples included in a residual signal of an current block, and an image coding step (S505) of coding, when the second flag indicates that the first scheme is used (Yes in S504), the image by using the first scheme.