In regenerative medicine, evaluation of bone mineral density using a microfocus X-ray generator could eventually be used to determine the degree of bone tissue regeneration. To evaluate bone mineral density against regenerated bone material, two low-energy X-rays are necessary. Herein, the acquisition of quasi-monochromatic, dual-energy soft X-ray and the subsequent medical application were examined using the K-absorption edges of two types of metal filters (i.e., zirconium and tin) in a microfocus X-ray generator. Investigation of the optimal tube voltage and filter thickness to form a quasi-monochromatic energy spectrum with a single filter revealed that a filter thickness of 0.3 mm results in an optimal monochromatization state. When a dual filter was used, the required filter thickness was 0.3 mm for tin and 0.2 mm for zirconium at a tube voltage of 35 kV. For the medical application, we measured quasi-monochromatic, dual-energy X-rays to evaluate the measurement accuracy of bone mineral density. Using aluminum as a simulated bone sample, a relative error of ≤5% was consistent within the aluminum thickness range of 1⁻3 mm. These data suggest that a bone mineral density indicator of recycled bone material can be easily obtained with the quasi-monochromatic X-ray technique using a microfocus X-ray generator.