The invention provides a cup shape grinding wheel for on-line roll grinding, which cup shape grinding wheel can easily secure the strength of base metal portions, and has a high degree of freedom of design for giving a required elastic function, and further has a structure suitable for being filled with a vibration absorbing material. The cup shape grinding wheel for on-line roll grinding is provided with grinding stone layers (3) arranged on the periphery of one surface of a disk shape base metal. The disk shape base metal has a first disk portion (1) having an annular grinding stone layer mounting surface, and a second disk portion (2) for supporting the first disk portion (1). The first disk portion (1) is fixed to the second disk portion (2) on its inside. The second disk portion (2) swells toward the outer peripheral side so as to form hollow spaces (5) below the first disk portion (1), and supports the first disk portion (1) by bringing the outer peripheral portion of the second disk portion (2) into contact with the outer peripheral edge of the first disk portion (1) from below. Elastic means (slits 1c (21c), 2c (22c)) are provided on the portions near the inside periphery and the outside periphery of the disk shape base metal, respectively.