To mix a plurality of fluids with a simple structure while a device is kept small-sized, in a micro-channel.

Fine particles 4 are filled in an outlet flow passage 2 to cause a turbulent flow. Each fine particle 4 has a shape to form fine voids between the fine particles and is filled between 1st projecting parts 3. Second projecting parts 5 are provided on the wall of the outlet flow passage 2 between the 1st projecting parts 3. The projecting part 3 and the projecting part 5 are formed to have alternate projecting direction. The projecting pats 3 and 5 are provided to narrow the thickness of a fluid layer on both sides of the contact surface of each fluid joined in the outlet flow passage 2. Fine repeating patterns 10 are provided in the outlet flow passage 2 and alternate patterns of the fine repeating patterns 10 and the projecting parts 11 are provided in the outlet flow passage 2.