To provide a member to be welded which is used in a friction stir welding method capable of preventing weld scrap generated on a surface of the member from being fixed thereto.

A probe 5 of a rotating body 2 is rotatably pushed into an abutting part 13 of members 6, 7 to be welded which are used in the friction stir welding method, and the abutting part 13 is subjected to the plastic flow. Thereafter, the members 6, 7 are cooled and hardened so as to be welded. A coating film 9 is formed on surfaces of the members 6, 7, which is capable of preventing weld scrap 14 formed of a part of the abutting part 13 subjected to the plastic flow which is outwardly raised.