Abstract: Planetary gear mechanisms require internal toothed gears in housings. A drive rotor and driven rotors are accommodated in a mixing space in a housing, and chemical inflow paths to the mixing space are formed in an upper portion of the housing. A mixture outflow path is formed in a lower portion of the housing. The mixing space is formed to allow the drive rotor and the driven rotors to rotate and to regulate the positions of the drive rotor and the driven rotors. Meshing the drive rotor with the driven rotors allows the driven rotors to rotate opposite to the rotating direction of the drive rotor accompanying the rotation of the drive rotor while the lower ends of the driven rotors are located above a bottom portion of the mixing space and the upper ends of the driven rotors are located below the lower surface of the lid body.