A radiation imaging apparatus including a tabletop onto which a patient lays down, a radiation imaging unit positioned below the tabletop and configured to detect radiation that transmits through the patient, a widthwise moving member supporting the tabletop and configured to move the tabletop in a widthwise direction, a moving mechanism unit including a lengthwise moving mechanism configured to move the tabletop in a lengthwise direction, the moving mechanism unit supporting the widthwise moving member and supporting the radiation imaging unit so as to be movable in the lengthwise direction, and a base unit supporting the moving mechanism unit.