The present invention discloses a focus detection device capable of reading a plurality of focus detection outputs in parallel. As an exemplary structure, the focus detection device includes a focus detection sensor having a plurality of output terminals for outputting, in parallel, analog data corresponding to focus states of multiple points in the field of a viewfinder, a multiplexer for arranging and outputting, in series order on the one terminal, the analog data output in parallel from the plurality of output terminals of the focus detection sensor, and an A/D converter for converting, to digital data, the analog data arranged in series order on the one terminal through and output from the multiplexer.