<p>Uniaxial tensile load is applied to the acrylic resin plat containing a fluorescent substance. A laser beam is irradiated to one point of the test piece where stress is generated, and photons of the test piece are detected with a photomultiplier. Change in photon number and fluorescence lifetime are obtained from photons detected by temporally correlated single photon counting method. By comparing with the load measured by the load cell, the relationship between stress and fluorescence is investigated.</p>