The purpose of this study is to evaluate the compressive strength of sintered titanium porous materials and their composites with biopolymers. The sintered porous material exhibits a network morphology due to the contact between particles connected in three dimensions. Titanium alloy powder (Ti6Al4V) was used as the raw material, and the powder was sintered using the spark plasma sintering process at a temperature of 750°C. Three types of biopolymers—polylactic acid, chitosan, and a chitosan derivative—were impregnated into the porosities of the sintered porous materials to produce the composites. To predict the compressive proof stress, the Gibson-Ashby formula was modified for these materials. This prediction of compressive strength is based on relative density in relation to porosity and relative compression strength measured experimentally. Compression tests were performed, and the proof stress was calculated. All experimental data were represented by prediction-fitting curves derived from the modified equation. The compressive strength characteristics of the porous Ti6Al4V alloys were clarified, and measurements of bending strength and tensile strength were conducted. The results were compared with the strength characteristics of bone, suggesting the potential applicability of the material as an implant.