PURPOSE: To enhance gas-liquid contact efficiency by finely dividing air bubbles, by sealing the upper end surface of a dispersing cylinder by a thin plate like valve plate and pushing up the valve plate only by the inflow of a gas-liquid fluid mixture from the lower part of the dispersing cylinder.

CONSTITUTION: When a gas-liquid fluid mixture 15 flows in, the end surface of a valve plate 8 is pushed up from a valve seat 12 by the pressure of said fluid mixture but, when the inflow of the fluid mixture is stopped, the valve plate 8 is contacted with the valve seat 12 of a dispersing cylinder 4 to hold a seal state. Especially, the valve plate 8 trembles like vibration at the inflow time of the gas-liquid fluid mixture 15 to be brought to a state repeating opening and closing and gas is mainly divided into fine gas bubbles. The finely divided gas bubbles increase a gas-liquid contact interface area to enable the lowering in the supply amount of the gas. Because the opening and closing of the valve plate is performed only by the mixing of the gas-liquid fluid mixture, the falling and invasion of a catalyst can be prevented regardless of the flow amount of the fluid.