Good mass transfer and high cell density culture are required for bioreactors using animal cells. These criteria can be met by fabricating a tissue in the bioreactor. In the present study, polypod particles were prepared using agarose, carrageenan, calcium alginate, and hydroxyapatite. The particles were then packed into reactors, and the reactors were filled with enzymatically cross-linked gelatin. Reactors with flow channels were then obtained upon dissolution of the gel particles. Cell adhesion, growth, and expression of organ (liver) function in the reactor were subsequently examined. Experiment using CHO-K1 cells suggested that the cells adhered and grew on the internal surface of the flow channels. HepG2 cells inoculated into the reactor expressed liver-specific functions over the 3-day culture period examined. Thus, the current findings demonstrate that the method developed can be applied to fabricate bioreactors to provide physiologically active substances and medical treatments for tissue engineering. Furthermore, this method was extended to the preparation of a hydroxyapatite-packed reactor by combining calcium alginate gel particles and hydroxyapatite. Therefore, this technique is expected to be applicable to both soft tissue models and hard tissue models such as bone.