A micro-bubble generating device is provided which is capable of mixing or dispersing micro-bubbles into a liquid with high stability and has a simple structure that permits reduction of a cost of manufacture. A first member and a first packing are superposed on each other on one side of a gas-permeable film, while a second member and a second packing are superposed on each other on the other side of the gas-permeable film. A pressurized gas delivered via a gas inlet of the first member flows through a fluid passage of the first packing, permeates through the gas-permeable film, and is ejected as micro-bubbles into a liquid flowing through a fluid passage in the form of a narrow shallow strip-like groove provided in the second packing.