Fluorine-doped $SmFeAsO_{1-x}F_x$ single crystals with the nominal value of x=0.2 were grown at $1350-1450^{circ}C$ under the pressure of 3.3 GPa by using the self-flux method. Plate-shaped single crystals in the range of a few-150 ${mu}m$ in their lateral size were obtained. The detailed crystal structure was analyzed by using the x-ray diffractometry. Superconducting transition temperature, determined by the resistive transition, of a single crystal was about 49 K with a narrow resistive transition width of ${sim}1$ K. A relatively sharp transition, a low residual resistivity, and a large residual resistivity ratio compared with those reported for $REFeAsO_{1-x}F_x$(RE=Sm, Nd) single crystals indicate the high quality of our single crystals.