In this invention, a grommet structure (21) in an incubator (1) includes a grommet attaching portion (22) provided to the enclosure (3) of the incubator (1) and a grommet member (13) attached to the grommet attaching portion (22). The grommet member (13) includes a longitudinal member holding incision (16) to hold a longitudinal member (15) such as an oxygen supply tube that extends through it. The longitudinal member holding incision (16) forms at least one substantially S-shaped shape (in other words, a substantially sine-curved shape) and/or a substantially waving shape. This invention can provide the grommet structure (21) in the incubator (1), in which the longitudinal member (15) such as an oxygen supply tube held by the longitudinal incision (16) of the grommet member (13) and extending through the incision (16) is less likely to move accidentally in the longitudinal direction of the incision (16) or in the longitudinal direction of the longitudinal member (15). Also, a gap through which the inside and outside of the enclosure (3) communicate with each other can be small even when the longitudinal member (15) extends through the incision (16).
