<p>An ink supply circuit (60) comprises followings: a sub-tank (23) which is connected with a printer head (22), has an ink reservoir chamber (31) formed internally, and has a liquid level detection section (40) for detecting the height position of the liquid level of ink mounted thereto; an ink supply path (19) which supplies the ink to the ink reservoir chamber (31); a decompression path (59) which decompresses the ink reservoir chamber (31); and a controller (13b) which judges whether a predetermined amount of ink is reserved in the ink reservoir chamber (31). The liquid level detection section (40) comprises followings: a case member comprising a section subjected to light projection which is adjacent to the outer surface with the ink positioned according to the amount of the ink stored in the ink reservoir chamber (31) and which light can enter; a light-emitting section which is disposed inside the case member and emits light from the inside of the section subjected to light projection toward the section subjected to light projection; and a light-receiving section disposed at an entering position of the light emitted from the light-emitting section and reflected by an outer surface.</p>
