1. A method of assembling a stator, comprising:providing a plurality of divided cores, each divided core including
a tooth having a circumferential width,
a divided back yoke extending from a radially outer edge of the tooth toward a first circumferential side and constituting a part of the divided back yoke, the divided back yoke having a radial width being less than or equal to the circumferential width of the tooth,
each tooth being aligned in a circumferential direction and extending toward radially inside from the divided back yoke, and
a connecting surface at an end of a second circumferential side opposite to the first circumferential side, the connecting surface being a plane or a convex surface extending from a side surface of the second circumferential side of the tooth to an outer circumferential surface of the divided back yoke; and
providing a plurality of annular coils, each annular coil having a center hole, each coil having a first center hole size of a first uniform width prior to being inserted around the tooth;
sliding the annular coil along each tooth, by moving the annular coil toward the tooth along the connecting surface so as to gradually enlarge the center hole to a second center hole size, the second center hole size being of a second uniform width, the second uniform width being uniformly greater than the first uniform width; and
coupling the plurality of divided cores each fitted with the annular coil to each other so as to be aligned in the circumferential direction.