PURPOSE: To reduce the size and cost by setting counter capacity so that the width of frequency variation corresponding to at least a balanced value is detected.

CONSTITUTION: When an article is placed on a measuring pan, etc., a vibrator 1 operates and varies in oscillation frequency from the frequency in an unloaded state. Both oscillation frequencies are counted by a counter 4 through a logical circuit 3 and counted values are inputted to a controller 5. An input part 6 consists of a ten-key, etc., and input various pieces of information to the controller 5. A setting part 8 sets weight (coefficient) per count. When the frequency variation width at the time of, for example, 2kg loading is 4,000 counts, the setting part 8 sets a coefficient of 2,000/4,000=0.5g/count. Then, the set coefficient is multiplied by the frequency variation width to calculate a weight value. Namely, when such a sensor that the frequency variation width at the time of 4kg loading is 4,000 counts is used, the set value is varied from the 0.5g/count to a 4,000/4,000=1g/count. The controller 5 calculates the frequency variation width, which is converted into weight and displayed 7.