PURPOSE: To reduce working time and obtain an amount of curvature with reproducibility by allowing a thermal analysis device to obtain the amount of bending which is performed manually as one of judgment of reliability of the device itself.

CONSTITUTION: Measurement data at two points indicating the range for obtaining the amount of bending are specified by a specifier which is constituted of a cursor specifier 3, a cursor operator's equipment 4, a specification point reader 5 out of measurement data which are stored in a data storage 1. A curvature width is retrieved automatically from the measurement data between two points which are specified by the specifier by a bending width retrieval equipment 6. The bending width retrieval equipment 6 calculates the amount of bending from the retrieved bending width.