An object of the present invention is to provide an oxygen isotope concentration method and an oxygen isotope concentration apparatus that can safely and stably supply ozone without increasing the size of the device. The present invention provides an oxygen concentration method including: a photoreaction step of irradiating a first mixed fluid (F1) in which oxygen and a diluent substance (DS) are mixed with a laser, selectively decomposing ozone containing an oxygen isotope, and generating oxygen containing an oxygen isotope, and obtaining a second mixed fluid (F2) in which the oxygen, the ozone, and the diluent substance (DS) are mixed; a liquid storage section introduction step of introducing the second mixed fluid (F2) into a liquid storage section (10) and liquefying it; and a separation step of introducing the second mixed fluid (F2) with hydraulic head obtained by liquefying the second mixed fluid (F2) and storing it in the liquid storage section (10), into a separation column (21), distilling the second mixed fluid (F2) which has liquefied, and separating into a third mixed fluid (F3) in which ozone and the diluent substance (DS) are mixed, and product oxygen (PO) in which oxygen isotope heavy components are concentrated; wherein the liquid storage section (10) can store the liquefied second mixed fluid (F2) without being affected by heat input.

The object of the present invention is to provide a stable isotope concentrating device that has high energy efficiency and can reduce equipment costs, and provides a stable isotope concentrating device including a distillation column group in which multiple distillation columns are cascaded, and the distillation column group includes: a tray column group including one or more tray columns; and a packing column group including one or more packing columns, and the packing column group is located on a secondary side of the tray column group.

The object of the present invention is to provide a stable isotope concentrating device that has high energy efficiency and can reduce equipment costs, and provides a stable isotope concentrating device including a distillation column group in which multiple distillation columns are cascaded, and the distillation column group includes: a tray column group including one or more tray columns; and a packing column group including one or more packing columns, and the packing column group is located on a secondary side of the tray column group.