Various foam specimens were prepared using foam injection molding with core-back method to polypropylene/glass fiber composite. Their mechanical properties and distribution of both foam cell and glass fiber were investigated. As the density of specimen decreased, both mechanical strength and tensile modulus decreased due to the increased formation of foam cell. However, the mechanical property was improved significantly by reinforcing with glass fiber. Uniform distribution of both foam cell and glass fiber was confirmed by X-ray CT and laser microscope. Foam injection molding of polypropylene/glass fiber resulted in improvement of mechanical property by glass fiber reinforcement as well as weight reducing by foaming.