As the technique of resistance spot welding became more and more advanced the factors hitherto considered secondary become more and more important. Among these factors the distribution of heat and temperature during resistance spot welding is particularly important in conjunction with thermal stress, strain and residual stress, strain problems. The analytical investigations upon the transient temperature due to resistance spot welding were made for the carbon steel plate and aluminum alloy plate. The numerical values obtained by the analytical investigation are nearly identical with the temperature distribution which obtained by D.J. Sullivan and some other experimental data. It was thought therefore useful to estimate the heat effect upon the material such as a residual stress and strain, metalurgical change, change in physical properties and etc.