PURPOSE: To expand the width in the shape recovery temp. of the shape memory alloy by subjecting a Ti-Ni alloy to intermediate temp. treatment in a furnace having a specified temp. gradient.

CONSTITUTION: A Ti-Ni shape memory alloy wire 1 is fixed in a ceramic tube 2, which is set in a furnace 4 via refractory bricks 3. A heating wire 5 is wound around the furnace and the furnace is heated; the winding distance in the heating wire 5 is suitably changed into a temp. distribution having a temp. gradient of 400 to 500°C. Then, the wire 1 is subjected to intermediate temp. treatment for about 30min. In this way, in the martensite inverse transformation starting temp. As and finishing temp. Af at heating and in the martensite transformation starting temp Ms and finishing temp. Mf at cooling, the distance between the As and Af point and the distance between the Ms and Mf point are expanded, by which the shape memory alloy in which position control is facilitates can be obtd.