Recently, it has been demanded to develop the lightened automobile with high stiffness and strength for the fuel economy and the vehicle safety performance. Therefore, it has been considered to apply the ultra high strength steel. A few reports indicate the fatigue strength of the spot welded joint using the high strength steel was not improved compared with the conventional mild steel. Moreover, it has been investigated the proper number of spot and the arrangement which were regarded the strength reliability for the energy saving and the cost reduction. In order to solve these problems, it is important to acquire the knowledge about the fatigue characteristics of spot welded joint. In this study, in order to investigate the fatigue characteristics, fatigue tests were conducted under the shear loading condition and internal fatigue crack behavior around the spot area was observed in detail. Test results showed that spot welded joints had the low fatigue strength compared with the strength of base metal. Additionally, specimens indicated the different fracture types; button fracture and base metal fracture. Then, 3-dimensional observation of the fatigue crack propagation was conducted on each fracture type. As this result, it was clarified spot welded joints used in this study require many cyclic loading to initiate the fatigue crack around the spot area. Furthermore their fatigue crack propagation indicates the similar behavior in major part of life independently of the stress level.