To provide an underground pipe unit that can prevent from coming off during transportation and construction, further can easily and quickly be assembled, and can surely prevent the deflection of an undergrount pipe while suppressing an increase in weight.

Projections 4 projecting outward than the outer surface of other portions of the underground pipe 1 are formed at a plurality of positions in the axial direction of the pipe. A plurality of the underground pipes 1 having the projections 4 are arranged substantially in parallel with each other so that the outer surfaces of the respective projections 4 abut against one another. Fixing means 5 are provided to integrate a plurality of the underground pipes 1 arranged substantially in parallel with each other in the horizontal direction or in the vertical direction or in the horizontal and vertical directions.