The (001) surface of InSb is the most common growth surface, forming a number of surface reconstructions depending on the both ratio of group III and V species presented on surface and substrate temperature. In the present work surface structures were studied using reflection high energy electron diffraction (RHEED). The c(4×4)↔(1×3) reconstruction transition was investigated in details. The intensity of fractional spots of c(4×4) structure was measured during the variation of antimony flux at different substrate temperatures. At the substrate temperatures of T<400 °C, hysteresis loop of fractional spot intensity appeared during the forward and reverse Sb flux variation, testifying that c(4×4)↔(1×3) transition is discontinuous first order phase transition. At the temperatures T>400 °C, hysteresis loop was not observed, that corresponds to continuous phase transition. It was shown that phase transition is analogous to the van der Waals transition. We developed a model to describe c(4×4)↔(1×3) transition in the framework of the lattice gas approximation. This model takes into account the complex nature of indirect interactions that result in the effective attraction between lattice gas cells forming surface reconstruction. The calculated surface state isotherms are in a good agreement with the experimental isotherms.