A sample rack conveying unit 30 includes a sliding rail plate 53, a presser 66, a first guide plate 55, and a second guide plate 56. The sliding rail plate 53 has a groove portion 71 formed along a track on which a sample rack 90 slides and along which the sample rack 90 is conveyed. The presser 66 passes through the groove portion 71 and presses the sample rack 90. The first guide plate 55 is arranged on an outer side of a curved portion in a radial direction. The second guide plate 56 is arranged on an inner side of the curved portion in the radial direction.