PROBLEM TO BE SOLVED: To attain a reduction in power consumption of a booster pump and an increase (efficiency) in outflow of a fluid treated on mixture by reducing pressure loss.SOLUTION: When three plate-like layers formed by aligning many through holes penetrating in the thickness direction are stacked, through holes of adjacently stacked plate-like layers are arranged alternately so that part of them may communicate with each other in an overlap state to form a plurality of first communication holes and second communication holes, and through holes of first and third plate-like layers are arranged alternately. A second communication hole formed of through holes of second and third plate-like layers is arranged in a separated state outside of a projection area of the first plate-like layer, through holes of the respective plate-like layers communicate with each other via the first and second communication holes arranged in a separated state in an extending direction of the plate-like layers and form a mixture treatment channel extending meanderingly and diffusedly toward the first and third layers.SELECTED DRAWING: Figure 1
