Quantum spin liquid (QSL) is a novel quantum state of matter, where spins are strongly entangled and highly fluctuating even at very low temperature. In this study, an organic QSL was newly synthesized, and the structure and physical properties were investigated. The antiferromagnetic interaction (J ≈ 24 K) detected between the spins was much smaller than that in the other organic QSLs, while the χ0 and γ values were larger. The results enable significant scalings, γ, χ0 ∝ 1/J for all the organic QSLs, which show the formation of the spinon energy band with the width of J. These findings provide good evidence of the spinon Fermi surface in the QSLs, where the spinon excitation follows the Fermi liquid behavior.