An ink jet printing apparatus includes an ink jet printing unit for executing ink jet printing on a printing medium by use of an ink jet printing head, a heat application treatment unit arranged below the ink jet printing unit for executing heat treatment to a printing medium after the execution of ink jet printing in the ink jet printing unit, and a heat insulating member arranged between the ink jet printing unit and the heat application treatment unit. Thus, this apparatus is made capable of preventing heat generated by the heat application treatment unit from producing any unfavorable effect that may invite the degradation of printing quality if such heat is transferred to the various members in the apparatus, such as the ink jet printing unit, the printing medium storage unit, or to the bending portion of a printing medium between the ink jet printing unit and printing medium storage unit.