The ⌳ 13 C hypernucleus was studied by measuring ␥ rays in coincidence with the 13 C(K Ϫ , Ϫ ) reaction. ␥ rays from the 1/2 Ϫ and 3/2 Ϫ states, which are the partners of the spin-orbit doublet states with a predominant configuration of ͓ 12 C g.s. (0 ϩ ) p ⌳ ͔, to the ground state were measured. The splitting of the states was found to be ⌬E(1/2 Ϫ Ϫ3/2 Ϫ )ϭϩ152Ϯ54(stat)Ϯ36(syst) keV. This value is 20-30 times smaller than that of single particle states in nuclei around this mass region. The j ⌳ ϭl ⌳ Ϫ1/2͓(p 1/2 ) ⌳ ͔ state appeared higher in energy, as in normal nuclei. The value gives new insight into the Y N interaction. The excitation energies of the 1/2 Ϫ and 3/2 Ϫ states were obtained as 10.982Ϯ0.031(stat)Ϯ0.056(syst) and 10.830Ϯ0.031(stat)Ϯ0.056(syst) MeV, respectively. We also observed ␥ rays from the 3/2 ϩ state, which has a ͓ 12 C(2 ϩ ) s ⌳ ͔ configuration, to the ground state in ⌳ 13 C. The excitation energy of the 3/2 ϩ state was obtained as 4.880Ϯ0.010(stat) Ϯ0.017(syst) MeV. Nuclear ␥ rays with energies of 4.438 and 15.100 MeV had similar yields, which suggests that a quasifree knockout of a ⌳ particle is dominant in highly excited regions.