In a stress measuring, system sensor driving power and a signal sensed by a sensor are transmitted and received in the form of a light pulse signal to thereby improve a noise resistant property as well as a measuring accuracy and reliability. The stress measuring system includes a sensor head disposed at a sensing location and a measuring device disposed at a location remote from the sensing location. The sensor head includes a sensor having a sensing section for sensing a change in stress as a change in the natural frequency of an oscillation string, an output section for outputting a light pulse sensing signal corresponding to the natural frequency sensed by the sensing section and a driving section for causing oscillation at the natural frequency of the oscillation system of the sensing section in response to a driving light pulse signal. The measuring device includes a measuring section for measuring the stress based on the frequency of the light pulse sensing signal and a creating section for creating the driving light pulse signal having the frequency following a change in the natural frequency based on the light pulse sensing signal. The sensor head is connected to the measuring device through optical fibers for transmitting at least the light pulse sensing signal and the driving light pulse signal.