A pneumatic tire comprises a tread portion provided with a central main groove, an outboard shoulder main groove and an inboard shoulder main groove extending continuously in the tire circumferential direction. The central main groove and the inboard shoulder main groove are each connected to grooves and/or sipes. The outboard shoulder main groove is widest and not connected to any grooves inclusive of a sipe or a very narrow groove. On both sides of the outboard shoulder main groove, there are formed sloping surfaces extending from the respective groove edges and merging into the tread surface. The width of each sloping surface is more than the depth thereof.