A high-sensitivity measuring instrument comprising at least two sensors for detecting the same characteristics by touching a substance being measured with a specified time difference, wherein the between detection signals taken out simultaneously from respective sensors is determined, the difference between characteristic values upon elapsing the specified time difference is determined from the difference between detection signals, a reference time of measurement and a reference characteristic value at that time are preset, a time axis having a time pitch of a specified time difference is set, and a measurement value is obtained at a point in time elapsing an arbitrary time pitch from the reference time. Objective measurement characteristics can be detected by the measuring instrument not in the form of difference or variation but as an absolute value with high accuracy and sensitivity.