In the component of a radiation detector, an upper end face of a pad formation protrusion provided on an upper surface of an MID substrate is equal in height to an upper surface of a photodiode array, first pads are provided on upper surfaces of photodiodes arranged in the photodiode array, respectively, second pads are provided on the upper end face of the pad formation protrusion, a bonding wire is provided between one of the first pads and corresponding one of the second pads, a wiring pattern is provided on the upper surface of the MID substrate, first terminals as many as the second pads and one second terminal are provided on a lower surface of the MID substrate, the second pads and the first terminals are electrically connected to one another in a one-to-one correspondence, and the wiring pattern is electrically connected to the second terminal.