A fuel instrument determination device comprising: a first obtaining section configured to obtain a slope of a change in a fuel flow rate in a first measurement period, the slope being obtained by dividing the change in the fuel flow rate in the first measurement period by time of the first measurement period; a second obtaining section configured to obtain a slope of a change in the fuel flow rate in a second measurement period which is different in length from the first measurement period; and a determiner section configured to determine a fuel instrument, using the slope of the change in the fuel flow rate in the first measurement period and the slope of the change in the fuel flow rate in the second measurement period, wherein the second measurement period includes a plurality of first measurement periods, wherein the determiner section is configured to determine the fuel instrument, depending on whether or not each of slopes of changes in fuel flow rates in all of the plurality of first measurement periods falls within a first range, and whether or not the slope of the change in the fuel flow rate in the second measurement period falls within a second range, wherein the first range is a range of the slope of the change in the fuel flow rate in which the slope of the change in the fuel flow rate is equal to or greater than a threshold m 1 and equal to or less than a threshold m 2, wherein the second range is a range of the slope of the change in the fuel flow rate in which the slope of the change in the fuel flow rate is equal to or greater than a threshold M 1 and equal to or less than a threshold M 2, characterized in that the slope of change in the fuel flow rate in the second measurement period is obtained by dividing the change in the fuel flow rate in the second measurement period by the time of the second measurement period, and the thresholds are related as m 1 ≦ M 1 < M 2 ≦ m 2. a first obtaining section configured to obtain a slope of a change in a fuel flow rate in a first measurement period, the slope being obtained by dividing the change in the fuel flow rate in the first measurement period by time of the first measurement period; a second obtaining section configured to obtain a slope of a change in the fuel flow rate in a second measurement period which is different in length from the first measurement period; and a determiner section configured to determine a fuel instrument, using the slope of the change in the fuel flow rate in the first measurement period and the slope of the change in the fuel flow rate in the second measurement period, wherein the second measurement period includes a plurality of first measurement periods, wherein the determiner section is configured to determine the fuel instrument, depending on whether or not each of slopes of changes in fuel flow rates in all of the plurality of first measurement periods falls within a first range, and whether or not the slope of the change in the fuel flow rate in the second measurement period falls within a second range, wherein the first range is a range of the slope of the change in the fuel flow rate in which the slope of the change in the fuel flow rate is equal to or greater than a threshold m 1 and equal to or less than a threshold m 2, wherein the second range is a range of the slope of the change in the fuel flow rate in which the slope of the change in the fuel flow rate is equal to or greater than a threshold M 1 and equal to or less than a threshold M 2, characterized in that the slope of change in the fuel flow rate in the second measurement period is obtained by dividing the change in the fuel flow rate in the second measurement period by the time of the second measurement period, and the thresholds are related as m 1 ≦ M 1 < M 2 ≦ m 2.