In this paper, a method for detecting kinematic constraints in a plane when the shapes of the grasped object and the environment are not given is presented.It is one of the important function for intelligent tasks of home, maintenance, assembly and disassembly robots. This method utilizes the displacement and force information obtained by“active search motion”of a robot. In reality, this information includes some uncertainties such as friction, slack and elasticity. A new neural network configuration for this detection is proposed. It consists of two multilayer networks (primary and secondary network) . The primary network learns the movable space (constraint) obtained by the search motion. By the generated link weights which reflect the movable space, the secondary network determines the type and the orientation of the constraint. Simulation and experimental results are presented and analyzed.