Nine or more forward speeds and one or more reverse speed are achieved by a planetary gear train of an automatic transmission for a vehicle. The planetary gear train includes: an input shaft, an output shaft, four planetary gear sets, and six control components. In particular, each of the four planetary gear sets includes a sun gear, a planet carrier, and a ring gear. Selective connections between the sun gears, planet carriers, ring gears, and a transmission housing are performed by the the six control components.