To provide a mechanism in which a bench plant is omitted, and the development of the material for a thin film stock is inexpensively and swiftly performed.

In the material designing device 100 for a thin film stock produced by continuous casting, a solidified structure obtained by a small-scale test by a casting apparatus 210 for a test is arranged by local temperature history obtained by performing casting simulation obtained by simulating the small-scale test, thus the specification of a large-scale continuous casting apparatus 220 for mass production capable of reproducing the same local temperature history is decided by casting simulation.