The present invention provides an incubator in which there is no particular need to interpose annular shaped packing, which is capable of substantially maintaining airtightness between a base frame positioned in the vicinity of an outer periphery of a service port and a service door, between the vicinity of the outer periphery of the service port and the service door. The incubator includes a substantially ring-shaped insertion groove that is formed in an inner face of the service door so as to substantially run along an outer periphery of the inner face, and a substantially ring-shaped outer peripheral portion that is formed to the base frame, and is configured such that a substantially ring-shaped leading end of the substantially ring-shaped outer peripheral portion can be inserted in a substantially ring shape into the substantially ring-shaped insertion groove.
