A stator includes a core-back portion, teeth portions, insulators, and coils. The teeth portions extend radially from a circumferential surface of the core-back portion. The insulators are respectively mounted to the teeth portions. The coils are respectively mounted to the insulators. A tip end of the tooth portion has a circumferential width equal to or smaller than that of a base end of the tooth portion. The tip end has an axial width equal to or smaller than that of the base end. The insulator includes a tube portion accommodating the tooth portion. The tube portion includes a first opening existing at the tip end and a second opening existing at the base end. The first opening has an axial width smaller than an axial width of the second opening in a state that each of the insulators is removed from each of the teeth portions.