A ball marker is provided with a pivotal member (2) that is constituted by a hinged portion (5), a shaft piercing portion (6) and an insertion portion (7) and allowed to pivot, and a main body (3) that allows the pivotal member (2) to be inserted therein and shaft-engaged thereto, and in this structure, when the hinged portion (5) is raised upright on the surface of the main body (3), the insertion portion (7) is also raised upright on the back surface of the main body (3) cooperatively, and when the hinged portion (5) is laid down on the surface of the main body (3), the insertion portion (7) is also laid down on the back surface of the main body (3) cooperatively, so that a housing section used for housing the insertion portion (7) is formed on the back surface of the main body (3); thus, the insertion portion (7) is made virtually flush with the back surface of the main body, with the hinged portion (5) and the insertion (7) portion being laid down. The objective of the present invention is to provide a golf ball marker that can be visually recognized easily even from a distant location when it is placed on the green face and used, and is superior in portability.