PURPOSE: To uniformly and efficiently distribute liquid by forming at least one notch at the upper end of the sidewall of a trough or at least one hole at the upper part of the trough, and inclining at least the part of the sidewall of the trough toward the outside.

CONSTITUTION: At least one notch 4 is provided at the upper end of the sidewall of a distribution trough 3 or at least one hole 10 is provided at the upper part of the trough 3. The part of the sidewall of the trough 3 is so formed as to incline toward the outside. Since liquid having overflowed from the notch 4 of the hole 10 flows down along the oblique surface of the sidewall of the trough 3, the liquid flows down while laterally diffusing on the oblique surface. Thus, since the liquid flowing out from one point of the notch 4 is laterally spread on the sidewall of the trough 3 and then dropped on a filler from the bottom, larger distribution than one notch can be performed, and hence the liquid distribution efficiency can be enhanced without increasing the number of the notches.