The Pomeron-nucleon coupling vertex is theoretically derived from the fundamental theory of strong interaction QCD. The empirical vertex βγμ F1 ( t) used commonly in diffractive processes with a coupling strength β =6.0 GeV-1 is initially obtained from QCD theoretically. Our study not only reproduces the Pomeron-nucleon coupling from QCD but also clearly shows the gluonic origin and glueball nature of Pomeron, which is a longstanding puzzle.From this investigation, we claim that Pomeron can be regarded as a Reggeized tensor glueball ξ(2230) with quantum numbers of IGJPC = 0+2++. Since the tensor glueball ξ(2230) lies on the Pomeron trajectory αp(t = M2ξ) = 2, the longstanding puzzle that no physical particle lies on the Pomeron trajectory, αp(t) = 1.08 + 0.20 GeV-2 . t, seems to be solved.