There were no experimental evidence for existence of a hadron with a quark configuration other than three quarks or a quark-antiquark pair although QCD does not forbid the existence of other combination such as qqqq or qqqqq. Since the LEPS at SPring-8 collaboration reported the first evidence for the Θ⁺ which has a quark configuration of uudds, extensive experimental efforts have been made to confirm the existence of the Θ⁺. In this paper, the experimental study of the Θ⁺ at LEPS together with the experimental situation and the future prospect are reported.