A device for capturing a radiation image of an object conveyed in a conveyance direction, the device comprising: a radiation source configured to output radiation; a carrier device configured to convey the object in the conveyance direction; a detector including a scintillator configured to convert radiation penetrating the object into scintillation light, a line scan camera configured to detect the scintillation light and outputting a detection signal, and an amplifier configured to amplify the detection signal at a predetermined set amplification factor and to output an amplified signal; an image generator configured to generate a radiation image based on the amplified signal; and an amplifier controller configured to set one of a first amplification factor or a second amplification factor, the second amplification factor corresponding to an amplification factor lower than the first amplification factor, as the set amplification factor based on a predetermined imaging condition, characterized in that the amplifier is connected in parallel to a first capacitance, the amplifier being also connected in parallel to a second capacitance through a switch; the amplifier controller is configured to set the first amplification factor that is based on the first and second capacitances as the set amplification factor by closing the switch, and to set the second amplification factor that is based on the first capacitance as the set amplification factor by opening the switch; the predetermined imaging condition is set based on the radiation image generated by the image generator under an environment in which the set amplification factor is set to the first amplification factor; the line scan camera is configured to perform image capture repeatedly in a state where the amplification factor is set to the first amplification factor and to acquire a plurality of images in the time axis direction, and the amplifier controller is configured to set the set amplification to the first amplification factor when a variation degree of luminance values of a plurality of pixels is smaller than a predetermined value and to the second amplification factor when a variation degree of luminance values of a plurality of pixels is larger than the predetermined value. a radiation source configured to output radiation; a carrier device configured to convey the object in the conveyance direction; a detector including a scintillator configured to convert radiation penetrating the object into scintillation light, a line scan camera configured to detect the scintillation light and outputting a detection signal, and an amplifier configured to amplify the detection signal at a predetermined set amplification factor and to output an amplified signal; an image generator configured to generate a radiation image based on the amplified signal; and an amplifier controller configured to set one of a first amplification factor or a second amplification factor, the second amplification factor corresponding to an amplification factor lower than the first amplification factor, as the set amplification factor based on a predetermined imaging condition, characterized in that the amplifier is connected in parallel to a first capacitance, the amplifier being also connected in parallel to a second capacitance through a switch; the amplifier controller is configured to set the first amplification factor that is based on the first and second capacitances as the set amplification factor by closing the switch, and to set the second amplification factor that is based on the first capacitance as the set amplification factor by opening the switch; the predetermined imaging condition is set based on the radiation image generated by the image generator under an environment in which the set amplification factor is set to the first amplification factor; the line scan camera is configured to perform image capture repeatedly in a state where the amplification factor is set to the first amplification factor and to acquire a plurality of images in the time axis direction, and the amplifier controller is configured to set the set amplification to the first amplification factor when a variation degree of luminance values of a plurality of pixels is smaller than a predetermined value and to the second amplification factor when a variation degree of luminance values of a plurality of pixels is larger than the predetermined value.