PURPOSE: To improve treatment performance of the method of removing pyrogen by performing ultrafiltration at specific temperature to remove pyrogen.

CONSTITUTION: A sample raw liquid tank 2, ultrafiltration unit 3, pipings and pump 4 are provided. The ultrafiltration unit 3 and pipings are heated by means of tape heaters 5 and the raw liquid tank 2 is heated by means of a heater 6 with temperature controller, in which temperatures of each of the unit, pipings and tank are always precisely controlled in the range of 50-60°C. Ultrafiltration is carried out at temperature in the range to remove pyrogen. As a result, treatment quantities can be increased without lowering the effect of ultrafiltration.