PURPOSE: To make the entire device compact and inexpensive, by obtaining the ratio between the loss pressure of a vortex flowmeter at a specified flow rate and the pulsating pressure of a fluid to be measured, and correcting the instrumental error of the vortex flowmeter in correspondence with the ratio.

CONSTITUTION: A pulsation-pressure correcting device is constituted by the following parts: a flow pipe 1, through which a fluid to be measured flows; a vortex yielding body 2; an operating circuit 3, which computes loss pressure S of a vortex flowmeter based on a vortex signal; a peak holding circuit 4, which detects pulsating pressure N in the flow pipe and keeps the value of the wave height; a dividing circuit 5, which computes a ratio N/S between the loss pressure S and the pulsating pressure N; and an adding circuit 6. The ratio N/S is obtained by the operating circuit 3, the peak holding circuit 4, the dividing circuit 5, and the like. The instrumental error of the vortex flowmeter is corrected in correspondence with the ratio. Thus the flow rate of the fluid to be measured can be accurately measured. The entire device can be made compact and inexpensive without requiring silencer as in a conventional device.