The present invention provides a system for pretreating sample that can unplug a rubber-plugged sample tube and a resin-plugged sample tube in one unplugging unit. The system for pretreating sample includes a sample rack on which a plugged sample tube can be mounted, a conveyor line for conveying the sample rack, and an unplugging unit that has a clamp device for holding the plugged sample tube at the time of unplugging and a plug chuck device for chucking the plug of the plugged sample tube held by the clamp device and unplugging the sample tube. The plug chuck device can unplug both the rubber-plugged and resin-plugged sample tubes. More specifically, the plug chuck device has a combination of an unplugging chuck having a suitable shape for unplugging the rubber-plugged sample tube and another unplugging chuck having a suitable shape for unplugging the resin-plugged sample tube.