Provided is a liquid detecting unit and a liquid jetting device that avoid generation of air bubbles and deposit of the components of ink due to electrolysis of the liquid when detecting liquid information. The liquid detecting unit is provided with an alternating current generation circuit for generating an alternating current to be applied to the liquid, a detection output generation unit for generating a detection output for detecting the liquid information based on a potential of a first connection point in the alternating current generation circuit and a potential of a second connection point in the alternating current generation circuit, and a detection unit for detecting the liquid information based on the detection output.