Hydroxyapatite coatings (HACs) have long been applied to orthopedic and dental implants made of titanium and its alloys because of their high biocompatibility and osteoconductivity. We have recently demonstrated that the charged surfaces on HAC induced by polarization enhance mineral deposition in simulated body fluid and osteoconductive capabilities in vivo. The present study evaluates the effects of the electrical polarization of HAC on surface characteristics and osteoblast adhesion. It was found that electrical polarization has no effect on surface roughness and crystallinity. Morphological observations and quantitative analyses of adhered osteoblasts on HACs revealed that the cell areas positively stained for actin, which indicates the degree of cell spreading, were distinctly larger on negatively and positively charged HAC than that on uncharged HAC.