The logarithmic vector fields (holomorphic vector fields tangent to given hypersurface) have been studied by Saito, Arnol'd, Lyashko, and Terao. Especially they studied the logarithmic vector fields i) along the arrangement of hyperplanes [6,9,10] and ii) along the discriminant of semiuniversal deformation of an isolated hypersurface singularity [6,1,4,11]. Here we shall study the module of the logarithmic vector fields along the bifurcation set of a semiuniversal deformation of an isolated hypersurface singularity and decide its structure. We shall give a method of explicit computation for its free base and a defining equation of the bifurcation set.