A radiation imaging apparatus includes a C-arm, a radiation source configured to irradiate a subject with radiation, and a two-dimensional detection device configured to detect the radiation having passed through the subject. The radiation source and the two-dimensional detection device are arranged to face each other across the C-arm, and at least one of the radiation source and the two-dimensional detection device is attached to the C-arm via a sub-arm that is rotatably connected to a frame of the C-arm.