To provide a differential pressure measuring device with a clogging diagnosis function of a lead pipe capable of discriminating and determining clogging between a high-pressure side lead pipe and a low-pressure side lead pipe, besides determining both-side clogging of the lead pipe.

This differential pressure measuring device with the clogging diagnosis function of the lead pipe is equipped with a reference data holding means for acquiring a differential pressure change output of a differential pressure transmitter to a diagnosis signal when the lead pipe is normal, and holding it as reference data; a measured data holding means for acquiring a differential pressure change output of the differential pressure transmitter to a diagnosis signal at a diagnosis time, and holding it as measured data; and a determination means for determining the clogging state of the lead pipe based on the reference data, the measured data and a set parameter.