At least part of a readout pattern including carrier collecting electrodes, capacitors, thin-film transistors, data lines and gate lines is formed by vapor deposition or printing. This is formed separately from a semiconductor thick film. The semiconductor thick film and readout pattern constitute a flat panel X-ray detector (FPD) is mounted in a case to form a unit. A weight reduction is achieved by using the semiconductor thick film in place of a conventional glass substrate. The FPD manufactured in this way is free from great restrictions in time of transport and use.