PURPOSE: To apply nearly uniform forming pressure to the whole formed item and consequently make it possible to obtain the favorable shape of the item even when locally ununiform cooling speed due to ununiform thickness develops by a method wherein the shape of a cavity, which is produced by material made of shape memory alloy, is adjusted by controlling the temperature of the material.

CONSTITUTION: A cavity 2 is produced by the opposed surfaces of forming cores 1a and 1b, in each of which a temperature controlling groove 3 circulating heating medium for controlling temperature is produced. During the injection and filling processes, the cores 1a and 1b are held at about 100 C and have cross-sectional forms represented by solid lines 8a and 8b due to their shape memory actions. If the shapes of the cores are held unchanged, no proper pressure is applied to the central part of the resin, which is filled in the cavity at high temperature, resulting in developing sinking. In order to prevent said sinking from developing, as the cooling of the resin proceeds, the cross-sectional forms of the cores 1a and 1b turn into the forms of the desired formed item represented by broken lines 9a and 9b at about 85°C due to the shape memory actions of the cores. As a result, nearly uniform forming pressure can be applied to the whole resin and consequently a formed item having a favorable form without sinking can be obtained.