A physical quantity measuring apparatus comprising: a plurality of physical quantity sensors (11, 12) of the same type, each of which is configured to detect a physical quantity at detection times at intervals of a predetermined time; a computing unit configured to calculate an output value according to physical quantities detected by the plurality of physical quantity sensors (11, 12) at each detection time; and a deciding unit configured to make a predetermined decision according to an output value calculated about an immediately preceding detection time and to physical quantities detected by the plurality of physical quantity sensors (11, 12) at a current detection time; wherein the computing unit is configured to calculate an output value at each time according to a decision result by the deciding unit, characterised in that the computing unit is further configured to calculate an average value of the physical quantities detected by the plurality of physical quantity sensors (11, 12) at the immediately preceding detection time, the deciding unit is further configured to determine whether the average value is present between a maximum value and a minimum value of the physical quantities detected by the plurality of physical quantity sensors (11, 12) at the current detection time, and the computing unit is further configured to set the average value of the physical quantities detected by two physical quantity sensors at the current detection time as the output value when the determination result is positive, and to set one of the physical quantitie detected at the current detection time, which is closest to the average value, as the output value when the determination result is negative. a plurality of physical quantity sensors (11, 12) of the same type, each of which is configured to detect a physical quantity at detection times at intervals of a predetermined time; a computing unit configured to calculate an output value according to physical quantities detected by the plurality of physical quantity sensors (11, 12) at each detection time; and a deciding unit configured to make a predetermined decision according to an output value calculated about an immediately preceding detection time and to physical quantities detected by the plurality of physical quantity sensors (11, 12) at a current detection time; wherein the computing unit is configured to calculate an output value at each time according to a decision result by the deciding unit, characterised in that the computing unit is further configured to calculate an average value of the physical quantities detected by the plurality of physical quantity sensors (11, 12) at the immediately preceding detection time, the deciding unit is further configured to determine whether the average value is present between a maximum value and a minimum value of the physical quantities detected by the plurality of physical quantity sensors (11, 12) at the current detection time, and the computing unit is further configured to set the average value of the physical quantities detected by two physical quantity sensors at the current detection time as the output value when the determination result is positive, and to set one of the physical quantitie detected at the current detection time, which is closest to the average value, as the output value when the determination result is negative.