PURPOSE: To save the labor and shorten the construction period by arranging an ultra-high strength concrete layer at the portion where tensile stress is generated and an ordinary concrete layer at the portion where compression stress is generated, and integrally sticking them.

CONSTITUTION: An ultra-high strength concrete layer 1 is arranged at the portion where bending stress is applied by a vertical load and tensile stress is generated, an ordinary concrete layer 2 is arranged at the portion where compression stress is generated, and both concrete layers 1 and 2 are integrally stuck. When this plain concrete member is used for a beam B, a U-shaped outer periphery section consisting of both inner and outer layers and a bottom layer of the beam B is formed with the ultra-high strength concrete layer 1, and the inner section is formed with the ordinary concrete layer 2. Economic cross section designing and mix designing can be performed.