The influence of electron-beam irradiation on the wettability of hydroxy apatites (HAP) has been investigated. The wettability was evaluated from the interfacial energy between HAP and water. It was measured by the contact angle of distilled water on HAP. Electron-beam irradiation increases the wettability. Based on the rate process, the influence of electron-beam irradiation on wettability is discussed. Using electron-beam irradiation, we can precisely control the surface condition of HAP.