To provide a marker which is excellent in cost, portability, storage ability, and is easily obtained in an easy-to-understand size, and can also be installed in any necessary place without disturbing spectacle.

This marker comprises two vertical stick members 2p, 2q and a sheet of member 4 displaying a mark thereon; horizontal stick members 3u, 3d have detaching part 5 detached to the vertical stick members 2p, 2q at both ends; the vertical stick members 2p, 2q have a positioning part 6 to position the detaching part 5; and the sheet member 4 is formed in a rectangle having inserting parts 7p, 7q, 7u, 7d in which each of the stick members 2p, 2q, 3u, 3d is inserted on the four sides.