Power consumption in a non-baffled agitated vessel with a double impeller was measured over a wide range of Reynolds number from laminar to turbulent flow regions. The power correlation for the double impeller was derived from the modification of the power correlation for a single impeller proposed by the authors. The power consumption in a baffled vessel was only measured in the turbulent flow region. The power consumption for the double impeller has the maximum value, which was almost twice the power consumption for the single impeller at larger ratio of impeller clearance to liquid depth than 0.35, and it took the minimum value at the impeller clearance ratio of 0.18-0.25. Mixing time in a baffled vessel with sonic types of double impeller was measured in the turbulent flow region using the decolorization method of sodium thiosulfate and iodine reaction. The minimum mixing time was observed at 0.1-0.2 of the ratio of impeller clearance to liquid depth for the two-stage paddle system, and 0.5-0.7 for the double impellers constructed with the pitched blade paddle. The relationship of mixing time to power consumption for the double impeller system coincided with that for a single impeller at the impeller clearance taking the minimum mixing time.