A prefabricated shower pan for installation on an installation site having a waste outlet hole includes a drain hole configured to communicate with the waste outlet hole of the installation site via a drain assembly, a shower pan floor having a slated surface towards the drain hole, at least one side wall surrounding and supporting at least a portion of the circumference of the shower pan floor, and an accommodation space disposed below the drain hole and configured to accommodate the drain assembly for connecting the drain hole in the shower pan floor and the waste outlet hole at the installation site, and the accommodation space extends to the at least one side wall, and an optional side wall opening is disposed at the at least one side wall.