Provided are a photoelectric conversion device, a method of manufacturing the photoelectric conversion device, and an X-ray image detector. A photoelectric conversion device at least includes a photodiode device. The photodiode device includes a lower electrode and an upper electrode, and a photoelectric conversion layer put between the lower and upper electrodes, where the photoelectric conversion layer includes a patterned edge surface, is smaller in size than the lower electrode and is placed on a surface of the lower electrode. The photodiode device further includes a protecting film covering at least the patterned edge surface of the photoelectric conversion layer. The protecting film except for an area where a contact hole is formed and the lower electrode are formed with a same-shaped pattern.