To form a sample holding part into a comparatively simple constitution and to contrive reduction of the cost of the sample holding part, by a method wherein when a sample held by the sample holding part of a shaft member is put in contact with a molten solder, a force to act on the sample is detached.

A upward and downward displacement by a sample holding part 42 of a sample 55 is transferred to an elastic plate member 51 provided at a measuring part 50 via a shaft member 41 and a coupling member 45. Thereby, in the measuring part 50, detection of a force to generate the displacement of the member 51 by a transducer built in the measuring part 50 is conducted, and at the same time, a detection output signal SD to respond to the detected result is formed and the signal SD is led out between one pair of output terminals 53a and 53B as a solderability measuring output signal to the sample 55. As a result, the sample holding part is formed into a comparatively simple constitution and reduction of the cost of the sample holding part is contrived.