To provide a valve failure detection device that can detect a mechanical failure of a valve.

A valve failure detection device includes liquid detection means that detects impedance between two electrodes 34, 35, and detects liquid, and channels 8 of liquid using an electromagnetic valve 6. The two electrodes 34, 35 of the liquid detection means are installed in the channels at both ends of the electromagnetic valve 6, respectively, so that they are brought into contact with liquid, and the phenomenon that opening/closing of the electromagnetic valve 6 causes difference in impedance between the electrodes 34, 35 is used.