There have been accumulating experimental evidences that several triangular organic materials, κ-(BEDT-TTF)2Cu2(CN)3, EtMe3Sb[Pb(dmit)2]2, κ-H3(Cat-EDT-TTF)2, exhibit quantum spin liquid (QSL), where any spatial symmetry breaking does not occur when it is cooled down to zero temperature due to the quantum fluctuation.The realization of QSL against a symmetry breaking Néel ordered state is one of longstanding issues in condensed matter physics.In the early stage, the geometrical frustration has considered to play important rule for the emergence of stable QSL.However, recent numerical studies have suggested that the ground state of the spin-l/2 Heisenberg model on the triangular lattice is 120 Néel ordered.