To provide a simple, inexpensive and easily handleable PET bottle-supporting device for automatically feeding water to a pet, and enabling miniaturization in distribution process and under preservation, and to provide a kit to be assembled.

The PET bottle-supporting device (10) is constituted of a pedestal frame (1) to be put nearly horizontally on a floor or the like, a vertical frame (2) to be nearly vertically attached to the pedestal frame (1), and a supporting frame (3) horizontally attached to the vertical frame so as to be nearly perpendicular the vertical frame (2), and supporting a PET bottle (7) by at least constraining the shoulder part of a PET bottle (7) so as to restrict the dropping of the PET bottle (7). As a result, the PET bottle (7) can be supported in a state in which the mouth (7a) of the PET bottle (7) is separated from the bottom face (6a) of a water container (6) to enable the water to be automatically fed to a constant water level in the water container (6). The PET bottle-supporting device (10) can easily be disassembled and assembled, and can be distributed as the kit to be assembled in a compact style of packing.