In order to provide an animal fixation device and an animal fixation method which are able to euthanize and fix the animal instantaneously and steadily, a columnar cage in which animal is arranged, a rotation mechanism configured to rotate the cage, an euthanizing gas supply mechanism configured to supply euthanizing gas into the cage, and a solid refrigerant supply mechanism configured to supply a solid refrigerant into the cage are provided. The euthanizing gas supply mechanism includes a gas manifold for euthanizing which is connected to the cage so that the euthanizing gas flows on an inner wall of the cage along a circumferential direction. The solid refrigerant supply mechanism includes a solid refrigerant supply line which is connected to the cage so as to be able to supply the solid refrigerant during rotation of the cage.