We discuss the production of the composite Higgs boson in topcolor models via the gluon fusion process. We consider the contribution of color-octet massive gauge bosons (colorons) strongly interacting with the top quark, in addition to nonstandard contributions of the top-Yukawa coupling and heavy colored fermions other than the top quark. In order to estimate the contribution of colorons, we derive the low-energy effective theory by eliminating colorons by using the equation of motion for colorons. We replace the composite operator (\bar{q}_L t_R)(\bar{t}_R q_L) in the effective theory by the composite Higgs operator. We then obtain the effective gluon-gluon-Higgs (ggH-) operator induced by colorons and find that its coefficient (A_{col}) is proportional to m_{dyn}^2/M^2, where M and m_{dyn} denote the coloron mass and the mass dynamically generated by colorons, respectively. The contribution of colorons A_{col} becomes comparable to the top-loop effect A_{top} for M=O(1TeV) and m_{dyn}=O(0.6TeV). Such a large dynamical mass can be realized in top-seesaw (TSS) models consistently with the experimental value of the top quark mass (m_t^{exp}), while the dynamical mass itself is adjusted to m_t^{exp} in topcolor assisted technicolor models (TC2). We find that the coloron contribution A_{col} can be sizable in a certain class of TSS models: the contribution of colorons (the top-loop) is dominant in the real (imaginary) part of the H->gg amplitude for the Higgs boson mass m_H of the order of 1 TeV. On the other hand, enhancement of the top-Yukawa coupling becomes important in TC2. We can observe signatures of the Higgs boson in TC2 with m_H \sim 200 GeV even at the Tevatron Run II as well as at the LHC. We estimate S/\sqrt{B}=3-6 for an integrated luminosity of 2 fb^{-1} and m_H=190 GeV at the Tevatron Run II.

11 pages, 1 figure, REVTeX; To appear in PRD. Discussion is improved