Organophosphorus compound and flame retardant agent comprising same, and method for producing organophosphorus compound

The present invention addresses the problem of providing: a novel organophosphorus compound which can impart flame retardancy to an amorphous resin without deteriorating the heat resistance and transparency of the amorphous resin even when added to the amorphous resin in a smaller amount, and which can be used for wide varieties of resins; a flame retardant agent comprising the organophosphorus compound; and a method for producing an organophosphorus compound. An organophosphorus compound represented by general formula (1) (wherein R 1 and R 2 independently represent a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 15 carbon atoms, or an alkylaryl group having 7 to 15 carbon atoms; R 3 and R 4 independently represent an alkyl group having 1 to 15 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 15 carbon atoms, an alkylaryl group having 7 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an aralkyloxy group having 7 to 15 carbon atoms, or an alkylaryloxy group having 7 to 15 carbon atoms, provided that R 3 and R 4 may be bound to each other to form a ring; and m and n independently represent 1, 2, 3 or 4); a flame retardant agent comprising the organophosphorus compound: and a method for producing an organophosphorus compound.