To provide an image forming device capable of preventing bubbles from being mixed into ink stored in a sub-tank with a simple mechanism.

A heating element 70 is arranged in front of an ink inlet 22Ka of an ink tank 22K. The ink (I) made to flow in from the ink inlet 22Ka is in contact with the central part of a plate-like erecting part 78 of the heating element 70 by directly colliding with it. An area of the erecting part 78 is larger than that of the ink inlet 22Ka. Consequently, all of the ink (I) made to flow in from the ink inlet 22Ka is directly in contact with the erecting part 78. The whole shape of the heating element 70 is formed into an L-shape. The heating element 70 is composed by embedding a nichrome wire 74 to the inside of a metal 72 (for example, aluminum or copper) excellent in heat conductivity.