PURPOSE: To eliminate transfer operation of a specimen accompanying modification of a carrier which was needed before and improve workability accompanying measurement by fitting a test tube as the carrier on heating to a measuring equipment of amount of electrical heating substance.

CONSTITUTION: An aqueous solution containing a specified concentration of endotoxin as an electrical heating substance is sampled by a test tube 2 which is made of glass which can be fitted to a measuring equipment of amount of electrical heating substance. The test tube 2 is used, heating is made at a specified temperature with a heating device 7 having a test tube fitting hole 8a..., the test tube 2 is used as it is, and the amount of remaining endotoxin is measured, thus obtaining thermal resistance.