A fine bubble generator may include an inlet, an outlet, a first fine bubble generation portion including a first flow path, and a second fine bubble generation portion including a second flow path. The first flow path may include a diameter-reducing flow path and a diameter-increasing flow path. The second flow path may include a guide flow path and a collision flow path disposed downstream of the guide flow path. A first bearing and a first impeller rotatably attached to the first bearing may be disposed on the collision flow path. The first impeller may include a disc disposed at a position at which the gas-dissolved water collides with the disc; a first rotation shaft disposed on a downstream surface of the disc and rotatably attached to the first bearing; and one or more first vanes disposed on an upstream surface of the disc.