PURPOSE: To develop a bidirectional TiNi series shape memory alloy by introducing a fault such as a hole into the alloy and thereafter repeating the cold plastic working and the heat treatment in case of the manufacture of the TiNi series shape memory alloy.

CONSTITUTION: Ti powder and Ni powder are made to an essential raw material and if necessary at least one and more kinds of the powder of Al, Sn, Zr, Mo, V, Nb, Ta, Mn, Cr, Fe, Co, Cu, Si and W, etc., are mixed. This is pressed in a prescribed shape, compacted and sintered in vacuum or in the gaseous inert atmosphere. A fault such as a hole is introduced into the sintered alloy at this time and the fault is dispersed and built-in by performing the working such as the cold rolling and furthermore the residual strain is dispersed and built-in by repeating the operation heating it at 900°C for 1hr in two and more times. The heterogeneous phase other than the TiNi basic phase is dispersed by controlling the oxygen concn. and the Ni basic composition and also a stress induction martensity phase is introduced into the inside of the crystalline grain.