To provide a ground liquefaction analyzing method using an FEM program capable of simply modeling the action of water resisting against the volumetric deformation of a constitution rule of soil when earthquake response analysis considering the effect of liquefaction on the sand ground or the like is performed using the FEM program of an one-phase system.

When the liquefaction of the ground is analyzed using the FEM program of the one-phase system, an elastoplasticity constitution rule of soil capable of expressing the effective stress accompanied by repeating shearing and the lowering of shearing rigidity is incorporated as the constitution rule of soil and the bulk modulus of elasticity of water is applied to a linear plane strain element or the value of a poisson ratio approximate to 0.5 and the shearing rigidity value obtained from the value of the poisson ratio and the bulk modulus of elasticity by calculation are applied to the linear plane strain element in place of the bulk modulus of elasticity of water to be modeled as a water element for expressing interstitial water and the constituent nodal point of the water element is communized with respect to the nodal point of the element of soil using the constitution rule.