To provide a U-shaped ditch connecting structure facilitating work of connecting U-shaped ditches in a butting state.

The front and rear of an abutting part of two U-shaped ditches made of synthetic resin are covered with a connecting cover 2 made of synthetic resin, from three ways of the inner surface, upper surface and outer surface, and a space between the front and rear ends of the connecting cover and the U-shaped ditches, or a space between the inner surface of the connecting cover and the U-shaped ditches is sealed with a caulking material 5. One of the outer surface of the U-shaped ditch and the connecting cover is provided with claws 4, and the other is provided with engaging grooves 3. The claws are fitted into the engaging grooves to connect two U-shaped ditches.