In our earlier work, a flexible fibermat consisting of a biodegradable composite with soluble silicate species, which has been reported to enhance bone formation, was prepared successfully using poly(L-lactic acid) and siloxane-containing calcium carbonate particles by electrospinning. The fibermat showed enhanced bone formation in an in vivo test. In the present work, to improve the hydrophilicity of skeletal fibers in a fibermat, they were coated with nanotubular aluminum silicate crystals, which have a hydrophilic surface that has excellent affinity to body fluids and a high surface area advantageous for pronounced protein adsorption. The nanotubes were coated easily on the fiber surface using an electrophoretic method. In a conventional contact angle test, a drop of water rapidly penetrated into the nanotube-coated fibermat. The culture test using murine osteoblast-like cells (MC3T3-E1) showed that the cell attachment to the nanotube-coated fibermat at an early stage after seeding was enhanced in comparison with that to the noncoated one. This approach may provide a new method of improving the surface of polymer-based biomaterials.