1. An X-ray image taking device, comprising: an emitting unit that emits an X-ray; a sensor that receives the X-ray on an image taking region thereof and converts the received X-ray into image data; a drive unit that drives the sensor; an X-ray detecting unit that sets a drive timing of the drive unit in accordance with a timing at which the X-ray emitted from the emitting unit is detected; and a control unit that controls the emitting unit, the drive unit, and the X-ray detecting unit, wherein the X-ray detecting unit is provided outside the image taking region of the sensor.