We demonstrate a quantum cascade laser (QCL) emitting at around 5.0μm with a peak power of 4.7W in room temperature (298K) continuous wave (CW) operation. The cavity length and the ridge width are 7.5mm and 6.5μm, respectively. The active core was grown by molecular beam epitaxy (MBE) with high AlAs quantum barrier layers designed to suppress the current leakage. The device achieved the maximum power of 10.2W and the maximum wall plug efficiency (WPE) of 22.7% in pulsed mode. High beam quality is achieved by single transverse mode (measured M^2<1.5) with CW power of 4W at 298K.