A sample-conveying system has first and second conveying paths which are separated from each other. A first transition base is located at a conveyance terminal end portion of the conveying path. A second transition base is located at a conveyance starting end portion of the conveying path. A mobile unit moves between the first and second conveying paths. The transition base is provided with a receptacle carrier and a rack carrier. The receptacle carrier transfers receptacles on the conveying path to a rack on the transition base. The rack carrier transfers the rack on the transition base onto the mobile unit. The transition base is provided with a rack carrier and a receptacle carrier. The second rack carrier transfers the rack on the mobile unit onto the transition base. The second receptacle carrier transfers each receptacle held in the rack to a holder in the conveying path.
