To provide a microbubble generation nozzle of simple structure.

The microbubble generation nozzle 1 comprises an outer cylinder 2 and first and second passage forming members 3, 4. The first and second passage forming members 3, 4 are set with tapered passages 5b, 6b faced to each other. The first passage forming member 3 is fixed to the outer cylinder 2 and second passage forming member 4 is axially adjustable in position. The first and second passage forming members 3, 4 are disposed away from each other, an annular space 10 is formed between the first and the second passage forming member 3, 4, an annular space 11 is formed between the first passage forming members 3 and outer cylinder 2. The annular space 11 is extended to a space with a triangular cross section between the outer cylinder 2 and the first passage forming member 3, and a gas introducing port 12 is disposed so as to be displaced upstream from the end of a tapered outer circumferential face 7b of the first passage forming member 3 positioned at a deep portion of the outer cylinder 2.