An oxygen absorbing agent has excellent oxygen absorbing properties and can absorb oxygen in an atmosphere, even under a moisture-free or substantially moisture-free atmosphere. The oxygen absorbing agent includes an alloy obtained by subjecting an alloy (X) including (A) at least one transition metal selected from the group consisting of manganese, iron, platinum, and copper group metals and (B) at least one metal selected from the group consisting of aluminum, zinc, tin, lead, magnesium, and silicon, to treatment with an alkali aqueous solution to elute and remove at least a part of the component (B) in the alloy (X), wherein the alloy (Y) has an X-ray diffraction profile satisfying a diffraction peak relationship.