PURPOSE: To detect the pressure of a gas at high accuracy irrespective of the type of the gas by disposing an exothermic body and a heat receiving body with the specific position relationship so as to face each other and calculating pressure with the use of both temperature detection values.

CONSTITUTION: The exothermic body (heating plate) 13 and the heat receiving body 10 are faced and installed in parallel in a vacuum chamber 23 whose pressure is measured. The interval between the exothermic body 13 and the heat receiving body 10 is set smaller than the average free travel of the gas at a vacuum degree in the vacuum chamber 23. Then temperature detectors 11 and 12 such as a thermo-couple are fitted on the exothermic body 13 and the heat receiving body 10, and respective detecting signals are led to an arithmetic unit 19 so as to execute the prescribed arithmetic processing, whereby the pressure in the vacuum chamber 23 can be detected. Thus the pressure can be detected irrespective of the type of the gas, and calibration in accordance with the type of the gas is made unnecessary.