A radiological imaging apparatus and method allows an operator to select between moving-picture imaging and still-picture imaging modes using the same apparatus so to provide radiological imaging having a picture quality equal to that of conventional radiological film imaging techniques but with a smaller, lighter and more compact equipment configuration. The apparatus employs photoelectric converters arranged in a two-dimensional matrix array for converting radiation into electrical signals, a read-out circuit for reading the signal output from the photoelectric converters, variable gain amplifiers upstream of an analog multiplexer and a buffer amplifier downstream of the multiplexer for outputting serially converted signals. The method involves setting the moving-picture mode gain Gf so as to be greater than the still-picture mode gain Gs, in order to obtain sharper images without exposing the subject to unnecessarily high levels of radiation.