A method for measuring an amount of a sublimate in real time with respect to a lapse of heating time, comprising: adhering the sublimate from a thermoset film during heating to a surface of a crystal oscillator using a nozzle inserted into a detection part; and measuring the amount of the sublimate from a change in a resonance frequency corresponding to the amount of the sublimate adhered to the crystal oscillator. In the method, the thermoset film may be formed on a silicon wafer and the measurement is performed while the thermoset film is heated by a heat source disposed under the silicon wafer; or the sublimate may be set so as to flow together with an airstream ascending toward an upper part of an enclosure covering the thermoset film, and the airstream directly contacts the crystal oscillator through the nozzle inserted into the detection part disposed in the path of the airstream.