A thermotherapy device is operated as an incubator or as an open care unit. The care unit has a bed for receiving newborns, which can be closed with a hood (3). At least one heat radiation source (4) is provided. The hood (3) is located between the bed and the heat radiation source (4) when the thermotherapy device is closed and the hood is at least partially transparent to the radiation originating from the heat radiation source (4). The device allows only a small temperature drop during the transfer from the open mode of operation into the closed mode of operation and vice versa.