[en] Interaction between Λ and N are composed of the following five forces, i.e. central force independent on spins, spin-spin force, spin-orbit force dependent on nuclear spins, spin-orbit force dependent on lambda particle spin and tensor force. In this paper, experimental study of the tensor force among the effective interaction between Λ and N in p-shell hypernuclei is reported. The tensor force can be evaluated from the level separation between the ground state doublets of the p_1/2-shell hypernucleus. The experiment was carried out on the D6 beam line of AGS at BNL as E930(2001). The γ-rays from ¹⁶_ΛO and ¹⁵_ΛN produced by ¹⁶O(K^-, π^-)¹⁶_ΛO reaction was measured by the Hyperball γ-rays detection system with germanium detectors for hypernuclei spectroscopy. According to the preliminary analysis of the experimental results, the following values were obtained that the separation between the ¹⁶_ΛO ground state doublet is less than 30 keV and the magnitude of the tensor force is about 0.03 keV. Further detailed analysis is on the plan. (S. Funahashi)