To prevent degradation in image quality at a boundary with an extension image and suppress a processing amount of extension processing.

An image encoding method for encoding an image having a resolution that is not a multiple of the size of a block to be encoded, includes: a generation step for adding, to the image, an extension image which is to be added to the image and whose absolute difference value between a boundary pixel at a boundary with the image and a pixel adjacent to the boundary pixel is equal to or greater than a predetermined value to generate an image to be encoded; and a deblocking filter step for disabling deblocking filter processing at the boundary between the extension image and the image for a locally decoded image of the image to be encoded.