An antenna unit includes a patch antenna and a case. The patch antenna includes a conductive antenna pattern and an antenna ground pattern that functions as ground of the antenna pattern and receives an electric wave. The case has dielectricity, the case being provided with the patch antenna. The antenna pattern is provided on an inner wall surface of a wall portion of the case. The antenna ground pattern is provided on an outer wall surface of a wall portion of the case and is positioned so as to face the antenna pattern.