A radiation image taking apparatus having a radiation detecting unit which includes a plurality of photo-electric conversion elements and converts radiation into an electrical signal, a plate-like support member which supports the radiation detecting unit, an analog circuit unit having at least one of functions of controlling the radiation detecting unit, receiving an analog signal from the radiation detecting unit, processing the analog signal, and converting the analog signal into a digital signal, a digital circuit unit having at least one of functions of controlling at least one of the other units and communicating with a unit outside the apparatus, and a power circuit unit for supplying power to at least one of other units. The analog circuit unit, the digital circuit unit, and the power circuit unit are formed on separate circuit boards, respectively, and the analog circuit unit and the digital circuit unit are arranged on the opposite side of the radiation detecting unit with respect to the support member.