In this study, longitudinal strain distributions of rebars in the uniaxial tension test are evaluated with an image processing method (IPM). The measurements of strain are conducted till rebar is ruptured. As a result of the test, the detailed longitudinal strain distributions of rebar in the tension test are clarified and the results show that the strain at necking region are almost 2-3 times of average strain in the gauge length of specimen. After the stress of rebar is reached at ultimate strength, the most of elongations are concentrated at necking region. In the other region except necking region, therefore, the strains are merely increased till the end of test. From these results, it is estimated that the necking region can make the over estimation of elongation of rebar, therefore, the estimation except the necking region can be suggested to evaluate the true elongation of rebar. Also the measured results with IPM are compared with the measured results by using conventional strain gauge. It is estimated that the IPM shows some noise in data, but the IPM has advantages to measure the strain distribution to the range of rupture. Therefore if the image acquisition of the better resolution and better quality are possible, it can be a good alternative measuring method for the strain measurement.