To provide a technology capable of diluting gas simply and surely, and a technology capable of measuring simply and surely, a high gas concentration exceeding a measuring limit.

This manifold for gas dilution having a plurality of gas introduction passages having the same sectional shape, and one gas sampling path having the same shape formed with each gas introduction passage is used. Preferably, the gas introduction passages are provided on each of n-angular faces of a regular n-angular prism (n is an integer of 3 or more) and the gas sampling path is arranged on either face of the upper bottom face and the lower bottom face of the regular n-angular prism.