To provide a method and a device for producing liquefied nitrogen capable of efficiently obtaining high purity liquefied nitrogen with low purity nitrogen gas as the raw material.

The device for producing liquefied nitrogen is equipped with a cryogenic separation device 11 for cryogenically separating a low purity nitrogen gas RN and separating a high purity nitrogen gas GN, and a gas liquefaction device 21 for liquefying at least a portion of the high purity nitrogen gas GN separated by the cryogenic separation device 11. The device includes a first circulation passage 23a and a second circulation passage 23b for merging nitrogen gas generated in the gas liquefaction device 21, for example, a first circulation nitrogen gas CN1 and a second circulation nitrogen gas CN2, respectively, with the low purity nitrogen gas RN, the gases CN1 and CN2 selected out of the first circulation nitrogen gas CN1 in an atmospheric state, the second circulation nitrogen gas CN2 in a low pressure state, and a third circulation nitrogen gas CN3 in a medium pressure state.