The former Beatle said on his "Out There Japan Tour 2014" site that he wanted to perform Sunday against doctors' orders, but his team wouldn't allow it.
He said his condition had not improved and apologized for letting his fans down.
The 71-year-old McCartney got sick Friday, and canceled his concert at the last minute Saturday. But he said he'd be well enough to perform Sunday and do an additional concert Monday.
It's unclear whether the canceled concerts would be rescheduled, or when McCartney would recover to carry out the rest of his tour.