To perform blood sampling under a suction pressure being desirable for a doner by selecting automatically the suction pressure of a vacuum blood sampling room from a plurality of levels based on the flow rate of blood sampled measured by a blood flow rate measuring means.

A blood bag is set on a bag receiving tray and a blood sampling tube is set in a channel of a tube holder and an opening/closing lid is closed and the amt. of blood sampling is selected by a switch for switching the amt. of blood sampling. A CPU 28 measures empty wt. of the blood bag from output of a wt. sensor and write it in a memory and determines the wt. of blood sampling. When suction pressure is selected by a switch for switching the suction pressure, the CPU 28 determines control pattern of the suction pressure. In addition, a vacuum pump 24 is actuated by the CPU 28 and while the flow rate of blood is operated based on passing time and wt. measured by a wt. sensor 31, a vent valve 26 is made ON/OFF and the vacuum blood sampling room is adjusted by selecting automatically the optimum suction pressure from a plurality of suction pressure levels to perform blood sampling under a suction pressure being suitable for each doner.