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SmB₆ is an example of Kondo insulator compound where hybridization between conduction and core band electron level induces a gap at low temperature. Recently this material system has emerged as a strong candidate for a realization of topologically nontrivial state of matter in strongly correlated system, the topological Kondo insulator, which can be novel platform for investigating interplay between nontrivial topology and correlation driven emergent phenomena in solid state system. While the property of surface conduction with bulk insulating nature at low temperature has been revealed through electronic transport measurement, until now, there has been no direct electronic transport measurement which shows spin momentum locking on the surface of SmB₆. In this presentation, I will discuss potentiometric spin voltage measurement performed on the surface of SmB₆. Applied current, temperature and an external magnetic field dependence of the spin voltage are consistent with spin-momentum locking property, which can support that the surface state of SmB₆ is metallic surface with chiral spin texture.