PROBLEM TO BE SOLVED: To provide a bed structure for a newborn, which hardly incurs the risk of displacement of a newborn accommodation cage with respect to a cage retainer 7, even when a handler carelessly puts his/her hand on the newborn accommodation cage with relatively great force.SOLUTION: A cage lock mechanism 61 capable of locking a newborn accommodation cage to a cage retainer 7 comprises a lock member 64 capable of moving between a cage unlocking position and a cage locking position.