The present invention provides a method of producing a carotenoid having 50 carbon atoms which comprises culturing, in a medium, a cell transformed with a mutant phytoene desaturase gene and obtaining the carotenoid having 50 carbon atoms from the culture. The mutant phytoene desaturase gene has an introduced mutation to encode a mutant phytoene desaturase having an enhanced activity to desaturate a carotenoid backbone compound of 50 carbon atoms.