Foldable miter saws and a folding method of miter saws are disclosed. The foldable miter saws includes a base unit, a worktable, and a cutting unit. The cutting unit includes a support arm pivotally mounted on the worktable, a saw blade, and a driver. The miter saw folding method includes the step of biasing the cutting unit relative to the base unit and the step of rotating the support arm relative to the base unit and the worktable to change the cutting unit from a working position to a folded position, thus reducing the vertical space occupied by the cutting unit and facilitating delivery, storage and package of the foldable miter saws.