To make it possible to monitor an instrumental error of a reciprocal type flow meter.

In a fuel supply machine management system, the reciprocal type flow meter 24 is formed such that four cylinders 62a to 62d project radially in a casing 60 at 90intervals in the X and Y directions. Monitoring a change in lower limit peak value of a flow change P1 that has the largest amplitude among flow changes P1 to P4 caused by the reciprocal movements of pistons 64a and 64d makes it possible to determine whether an instrumental error of the flow meter 24 has changed or not. The control circuit 16 of the meter 12 monitors from the data about the flow change a change in the lower limit value of pulsation with the lapse of time. When a change in lower limit value of the pulsation is detected, the control circuit 16 determines that an abnormal state occurs, and informs of the abnormal state of the reciprocal type flow meter 24.