PURPOSE: To allow measurement of dielectric while enhancing accuracy and to simplify the measuring work.

CONSTITUTION: A thin film to be tested is held between a fixed plate 47 and a rigid pad 51 pressed elastically by an O-ring 49. A load cell 27 is elevated with respect to the thin film thus secured. When a steel ball 33 carried on the upper end of the load cell 27 comes into contact with the thin film, the thin film is subjected to compressive load which drops abruptly upon breakage of the thin film. Flexibility of thin film is determined based on the moving distance of the load cell 27 after contact with the thin film before breakage thereof and the compressive load at the time of breakage.