To provide a coffin for a pet animal to be used in cremation when such a pet animal as a dog, cat, rabbit or bird dies, hardly damaging a burner of a cremator with heat when the coffin is burned, capable of being accommodated in the cremator as it is when cremated, and permitting picking-up of cremated bones.

The coffin is shaped as a slender rectangular parallelepiped with a lid board. A notch or a flame-penetrating part equivalent to the notch is formed on a side panel facing the burner of the cremator when the coffin is stored in the cremator, and an auxiliary panel for closing the notch or flame-penetrating part is attached detachably or openably/closably. The coffin is preferably assembled by insetting without using clamps.