Laser sheet and digital camera was used for 2- dimensional visualization of the unsteady flow between corotating disks in air with a cylindrical enclosure. Geometric parameters are gap height between disks, and gap distance between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly. It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on height(H) between disks which is defined as ReH = ÙRH/v ranging from 7.96×102 to 1.43×104, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.