Evolution of TiN inclusion in solid state Fe-based alloy during heating at 1 473 and 1 673 K was studied by using Fe-36Ni alloy to avoid any unexpected influence of austenite-ferrite phase transformation of alloy on the observation of TiN inclusions in post-annealed samples. Average size of fine TiN inclusions smaller than 2 μm firstly decreased but changed to the increasing tendency during heating at 1 473 K, reflecting the initial dissolution of TiN inclusion in Fe-Ni matrix followed by gradual growth of inclusion by Ostwald ripening. On the contrary, heating at 1 673 K resulted in the monotonous decrease in average size of TiN inclusion in the size range up to 5 μm. It was considered that above mentioned different TiN inclusion evolution during heating at 1 473 or 1 673 K was due to the different solubility of TiN depending on temperature; thermodynamic calculation revealed that approximately 40% of TiN inclusion existing at room temperature may dissolve at 1 673 K whereas only few may dissolve at 1 473 K.