There is provided a method of generating nitrogen which includes cryogenically separating compressed air introduced into a high-pressure column 11, storing liquid air 13 in a bottom portion of the high-pressure column 11 and taking nitrogen in gaseous form from an upper portion of the high-pressure column 11, introducing the liquid air 13 stored in the bottom portion of the high-pressure column 11 into a low-pressure column 12, cryogenically separating the liquid air 13 introduced into the low-pressure column 12 and storing oxygen-enriched liquid air 22 in a bottom portion of the low-pressure column 12 and taking nitrogen in gaseous form from an upper portion of the low-pressure column 12 as a product gas. Liquid air 13 taken through an extraction pipe 20 is introduced into a portion of a rectification part 12a of the low-pressure column 12 in which the number of theoretical plates from a column bottom side is set within the range of one to ten.