To provide a contact cover used for an incubator for observation by a microscope, preventing the formation of spaces between the inner surface of a lens insertion hole and object lens, allowing precise management of temperature, humidity and the like of the environment in the space accommodating samples, and not requiring the production of a sliding contact cover with different dimensions of lens insertion hole diameter for each diameter dimension of object lenses, and to provide an incubator for observation by the microscope provided with the sliding contact cover.

A sheet 5 for the sliding contact cover 3 is formed from silicone rubber, which is a transparent material, and is flexible. The sheet 5 has a thin disk shape, and a circular lens insertion hole 7 is formed in the center thereof. The object lens T is inserted into the lens insertion hole 7. Since the sheet 5 is flexible, the diameter of the lens insertion hole 7 is expanded slightly by the lens barrel of the object lens T, and the inner surface of the lens insertion hole 7 adheres to the outer surface of the lens barrel of the object lens T. The state is such that no space is formed between the inner surface of the lens insertion hole 7 and the object lens T.