Disclosed is a sample processing apparatus that comprises a rack with positions to hold sample tubes, the rack including a rack identification suited to a kind of sample tube, a rack set unit that accepts the rack in a detachable manner, a tube transfer unit with mechanical movement to grab and take out each sample tube from a rack held in the rack set unit, a rack detector comprising a sensor to detect the rack identification of the rack held in the rack set unit, and a controller that controls movement of the tube transfer unit based on a detection result of the rack detector.