PROBLEM TO BE SOLVED: To provide a liquid level confirmation device of an air trap chamber for artificial dialysis excellent in a liquid level confirmation effect due to a holder of the air trap chamber being attached by a liquid confirmation mark.SOLUTION: There are provided a holder 10 having an engagement recess 10a for holding an air trap chamber 7, and a holding member capable of horizontally holding the holder 10. A liquid confirmation mark 17 is displayed within the engagement recess 10a of the holder 10. In a mounted state of the air trap chamber 7 on the engagement recess 10a, when the air trap chamber 7 is empty, the liquid confirmation mark 17 can be directly visually observed through a transparent casing of the chamber 7, and in a state in which a liquid surface of a transparent liquid P inputted in the air trap chamber 7 reaches a proper water level W2, the liquid confirmation mark 17 can be visually observed so as to be three-dimensionally viewed through the transparent casing of the air trap chamber 7 and the transparent liquid P.SELECTED DRAWING: Figure 4
