A plastic frame includes: a first frame portion having a surrounding structure; and a second frame portion having an outer edge part and an inner edge part opposite to the outer edge part, and having a first surface and a second surface between the outer edge part and the inner edge part. The outer edge part is joined with the first frame portion in such a manner that the first frame portion and the second frame portion are connected to form an L-shaped groove when viewed in a sectional view, and that the first surface of the second frame portion is an inner face of the L-shaped groove and the second surface is an outer face of the L-shaped groove. A beveled surface extends between an end face of the inner edge part and the first surface.