Abstract: A plastic pivot bush for swingably holding upper and lower spherical surface portions with respect to an equator of a spherical pivot, includes an upper concave spherical surface, a main body connected onto the upper concave spherical surface to enclose the remaining portion of the spherical pivot and having therein a cylindrical surface with a lower end thereof opened up, and an elastic thin piece originating from the boundary between the upper concave spherical surface and the cylindrical surface and provided with an opening at the center of a lower portion thereof. The elastic thin piece is split into a plurality of pieces by a plurality of slits extending in the longitudinal direction. The main body has at an outer periphery thereof an annular groove engageable with a mounting hole of the arm.