Conventional conveying lines have required building according to the particular shapes of test tube racks and test tube holders. For this reason, at least two types of dedicated lines, one for test tube racks and one for test tube holders, have been needed in one system, so there has been a tendency for systems to be complex in structure and disadvantageous in cost. To solve these problems, this invention provides a sample conveying system designed so that test tube racks and test tube holders can move on the same line, and high in both cost-effectiveness and reliability.