A package 10 for cell-containing material includes an inner bag 12 and an outer bag 16. The periphery of the inner bag 12 except an opening 14 is sealed. The periphery of the outer bag 16 except an opening 24 is sealed. The outer bag 16 contains the inner bag 12 such that the opening 14 faces outward. A portion of the opening 24 outside the inner bag 12 is sealed and forms an outer bag sealed portion 28. A portion of the opening 24 that overlaps the inner bag 12 is sealed and forms an inter-bag sealed portion 18. A space surrounded by the outer surface of the inner bag 12 and the inner surface of the outer bag 16 is a sterilized closed space 20. The material of the inner bag 12 and the material of the outer bag 16 are selected such that the adhesive strength of heat sealing of the inner surfaces of the opening 14 of the inner bag 12 is greater than the adhesive strength of the inter-bag sealed portion 18 and the adhesive strength of the outer bag sealed portion 28.
