The present invention relates to a medical liquid-pressure-detecting device capable of detecting both the negative pressure and the positive pressure of liquid, whereby the misconnection of the device to a liquid flow route can be prevented. A medical liquid-pressure-detecting device (5) includes a chamber unit (6) having an inlet (6aa) from which liquid flowing in a flow route is taken in and an outlet (6ab) from which the liquid is discharged, the chamber unit (6) being capable of storing the liquid by a predetermined amount； and a diaphragm (7) dividing an inside of the chamber unit (6) into a liquid chamber (S1) that stores the liquid and a gas chamber (S2) that stores a predetermined gas, the diaphragm (7) being deformable in accordance with a pressure of the liquid in the liquid chamber (S1), the medical liquid-pressure-detecting device (5) being capable of detecting a pressure of the liquid in the flow route on the basis of a change in the pressure in the gas chamber (S2) that is caused by the deformation of the diaphragm (7). The diaphragm (7) includes a negative-pressure-detecting region (B) that deforms toward one side when a negative pressure is generated in the liquid stored in the liquid chamber (S1), and a positive-pressure-detecting region (A) that deforms toward an other side when a positive pressure is generated in the liquid stored in the liquid chamber (S1).
