To provide a standard volume pipe which can obtain a high-precision standard volume.

The multiplex standard volume pipe 31 comprises a main inner pipe 32a through which a test liquid flows and in which a moving element 40 moves in a predetermined section thereinside, other inner pipes 33a, 34a, 35a, 36a, 43a, outer pipes 32b, 33b, 34b, 35b, 36b, 43b which cover the entire these inner pipes, and a fluid supply means 38 which allows a fluid to flow inside the outer pipes to allow the entire outside of the inner pipes to be exposed to the fluid. The multiplex standard volume pipe 31 is configured such that the fluid is allowed to flow in a direction opposite to the flow direction of the test liquid and that the predetermined section in which the moving element 40 moves is of the straight pipe type.