A core case unit (100) includes: an annular case (1) which houses a magnetic core (4); and a bobbin (2) around which a wire is to be wound, wherein the bobbin (2) includes a cylindrical portion (5) around which the wire is to be wound, inner flanges (6) provided at opposite ends of the cylindrical portion, outer flanges (7) provided on an outer side of the inner flanges with a space being left which is capable of containing a wire end portion, and a gear portion (8) provided on an outer side of at least one of the outer flanges for receiving rotational force, the bobbin being rotatably supported on the case at the cylindrical portion, an outside diameter of the outer flanges (7) is greater than an outside diameter of the gear portion which is defined by an addendum circle, and the inner flanges (6) and the outer flanges (7) have a recessed portion (15, 16) through which a wire end portion is to be passed.