A resin structure includes a first resin body, and a second resin body. The second resin body is fit to an outer surface of the first resin body while being slid to one side in a sliding direction along the outer surface of the first resin body. The first resin body and the second resin body form a water stop structural unit extending in the sliding direction in a state where the second resin body is fit to the first resin body. The water stop structural unit includes a first water stop structure in a first region located at the one side in the sliding direction, and a second water stop structure in a second region located at the other side in the sliding direction with respect to the first region.