A fatigue life estimating method for a spot welded structure is provided comprising the steps of providing a shell model of a spot welded structure for a finite element method analyzing process, calculating the nominal structural stress on a nugget as the center of the spot welded structure using a disk bending theory and a two-dimensional elastic theory of the elastodynamics with the partial loads exerted on the nugget and the deflection on the circumference of a circle, D in diameter, in which the nugget is located, which have been calculated by the finite element method analyzing process of the shell model, and estimating the fatigue life of the spot welded structure from the nominal structure stress. According to the method, the fatigue life of the spot welded structure can be estimated easily, readily, and accurately.