To provide the mounting structure of an external facing material in which waterproofness, workability or the like is improved.

The mounting structure of the external facing material A is composed of the external facing material A and a waterproofing-combining fixture B formed of a batten section 6, a waterproof piece 7 in which both left-right end sections of the batten section 6 are projected upwards, a lower piece 8 in which the lower edge of the batten section 6 is projected upwards, a locking piece 9, a locking groove 10 formed of the lower piece 8 and the locking piece 9, an upper piece 12 in which the upper edge of the batten section 6 is bent and projected upwards, a supporting piece 13, a supporting groove 14 formed of the upper piece 12 and the supporting piece 13, a lower piece 15 in which the front end of the supporting piece 13 is projected upwards, an engaging piece 16 and an engaging groove 17 formed of the lower piece 15 and the engaging piece 16. The waterproofing-combining metal fitting B is fixed onto the rears of joint sections at the left-right connecting sections of the external facing material A, the lower connecting section 2 of the external facing material A is inserted into the retaining groove 10, and an upper connecting section 3 is inserted into the supporting groove 14 in the joint sections, and approximately the central section of the lower connecting section 2 of the external facing material A is inserted and fixed into the engaging groove 17 of the waterproofing-combining fixture B at a lower stage.