To provide a mop yarn mounting base facilitating mounting and removing a mop handle.

A body 1 is formed in an elongated shape of a substantially rectangular parallelepiped, and a mop yarn is mounted on the lower side. A sandwiching part 2 of a rectangular parallelepiped shape is formed at the upper center, and a laterally elongated rectangular insertion hole 7 is provided vertically downward from the upper surface in the sandwiching part 2. Cuts 9 are provided inward from both ends in the sandwiching part 2. A handle mounting body 11 is prepared. The upper part of the handle mounting body 11 is formed as a cylinder 12, and the lower end of a handle is inserted into and mounted to the cylinder 12. A square insertion piece 14 just fitted in the lateral insertion hole 7 is formed at the lower part of the handle mounting body 11. A small cut 15 is provided inward from the outside in the respective insertion pieces 14. Left and right locking pieces 16 having horizontal pieces 17 are prepared. The insertion pieces 14 of the handle mounting body 11 are inserted into the respective insertion holes 7 of the body 1, and the respective horizontal pieces 17 of the left and right locking pieces 16 are pushed in the small notches 15 of the insertion pieces 14 from the cuts 9 of the sandwiching part 2.