A medical liquid-pressure-detecting device capable of detecting both the negative and positive pressure of liquid, whereby the misconnection of the device to a liquid flow route can be prevented. A medical liquid-pressure-detecting device includes a chamber unit having an inlet that liquid flowing in a flow route is taken in and an outlet that the liquid is discharged, the chamber unit storing the liquid by a predetermined amount； and a diaphragm dividing the chamber unit into a liquid chamber and a gas chamber, the diaphragm being deformable in accordance with a pressure of the liquid, the medical liquid-pressure-detecting device detecting a pressure of liquid in the flow route on the basis of a change in the pressure in the gas chamber that is caused by the deformation of the diaphragm that includes a negative-pressure-detecting region that deforms toward one side when a negative pressure is generated in the liquid stored in the liquid chamber, and a positive-pressure-detecting region that deforms toward an other side when a positive pressure is generated in the liquid chamber.
