A radiation detector includes a sensor substrate in which a plurality of pixels for accumulating electric charges generated in response to light converted from radiation is formed in a pixel region of a flexible base material; a conversion layer that is provided on a first surface provided with the pixel region of the base material and converts the radiation into light; an absorption layer that is provided on a side opposite to a side to which the radiation is radiated in a laminate in which the sensor substrate and the conversion layer are laminated and absorbs influence of irregularities generated on the conversion layer on the sensor substrate; and a rigid plate that is provided on a side of the absorption layer opposite to a side facing the laminate and has a higher stiffness than the sensor substrate. Provided are a radiation detector and a radiographic imaging apparatus capable of improving the quality of a radiographic image.