A phenomenological model of the transition from the quark-gluon phase to the hadron phase is presented on the analogy of the BCS theory. The massive current-quarks constitute the quark Cooper-pair i.e. the hadron at T_c = 150〜200 MeV. The order parameter of qq-pair takes a value in the range from 0.4 to 0.2 GeV. An experimental-verification method of the present model in the heavy-ion collision is proposed.
