A sample processing system includes a sample vessel holder including a disk-shaped base section disposed so as to have a central axis extending in a vertical direction and a sample vessel holding section that is formed coaxially with, and above, the base section for holding a sample vessel in an upright posture. A conveyor conveys the sample vessel holder 1 placed thereon; and a holding plate is disposed so as to extend along an outer peripheral portion of a columnar space that has a central axis extending in the vertical direction, and is disposed at a position above a space past which the base section of the sample vessel holder moves along the conveyor and at a position past which at least the sample vessel holding section moves. This enables individual conveyance processing to be performed for each of multiple sample vessels.