An incubator is provided that prevents damage to the arm of an operator when an arm abuts against the upper end segment of a baby guard relatively hard while inserting the arm into an infant accommodation space. The walls of the baby guards around the infant accommodation space have bent segments that are sufficiently strong to serve as a guard structure on the periphery of the infant accommodation space. Each of the bent segments in the upper end segments of the walls includes an inclined segment and a substantially horizontal segment integrally connected to a distal end of the inclined segment. At least some of the walls can pivot between upward and downward positions, thereby closing or revealing cassette trays.
