Porous titanium has long been desired as a bone substitute material because of its ability to reduce the stress shielding in supporting bone. In order to achieve the various pore structures, we have evolved a moldless process combined with a space holder technique to fabricate porous titanium. This study aims to evaluate which pore size is most suitable for bone regeneration using our process. The mixture comprising Ti powder, wax binder and PMMA spacer was prepared manually at 70 °C which depended on the mixing ratio of each group. Group 1 had an average pore size of 60 μm, group 2 had a maximum pore size of 100 μm, group 3 had a maximum pore size of 200 μm and group 4 had a maximum pore size of 600 μm. These specimens were implanted into rabbit calvaria for three and 20 weeks. Thereafter, histomorphometrical evaluation was performed. In the histomorphometrical evaluation after three weeks, the group with a 600 μm pore size showed a tendency to greater bone ingrowth. However, after 20 weeks the group with a pore size of 100 μm showed significantly greater bone ingrowth than the other groups. This study suggested that bone regeneration into porous titanium scaffolds is pore size-dependent, while bone ingrowth was most prominent for the group with 100 μm-sized pores after 20 weeks in vivo.