Thermography has been found to be useful for detecting the local variations in temperature of paper sheet under strain. The changes in temperature images during the course of tensile straining could describe the local deforming and fracturing process of paper. A thermal deformation pattern of well formed paper was locally uneven, but uniform wholly throughout the specimen. On the other hand, the deformation pattern of poorly formed paper was uneven in micro and macro scale at the early stage of its plastic deformation region. However, the deformation pattern was fairly uniform through the specimen at the later stage of its plastic deformation.