There can be provided an incubator (11) which relatively readily stores a cassette tray (61) in a cassette tray accommodation space (62) or takes out the cassette tray (61) from the cassette tray accommodation space (62) through one of a plurality of tray loading/unloading ports (63a-63c) even if a doctor or nurse performs an operation in a region including the outside of the cassette tray accommodation space (62) and its vicinity or even if a sophisticated article such as a sophisticated medical apparatus exists in the region including the outside of the cassette tray accommodation space (62) and its vicinity. In this incubator (11), the cassette tray accommodation space (62) includes at least two tray loading/unloading ports (63a-63c) of a front tray loading/unloading port (63a), a rear tray loading/unloading port, a left tray loading/unloading port (63b), and a right tray loading/unloading port (63c).