The stabbing was reported at 7:08 p.m. near Eddy and Taylor streets, where the driver had pulled over his 31-Balboa bus after a passenger said someone on board had a knife, police spokesman Officer Gordon Shyy said.
The 52-year-old driver called police, but while waiting for officers to arrive, the armed suspect approached him demanded that the bus continue on its route, Shyy said.
The driver saw the knife in the suspect's hand, then tried to get the suspect off of the bus but was stabbed in the leg, according to Shyy.
Police arrived and arrested the suspect, identified as 47-year-old David Choy, a San Francisco resident. He was booked into custody on suspicion of assault with a deadly weapon, making criminal threats, resisting arrest, probation violation and on multiple local warrants, Shyy said.
The bus driver was taken to a hospital to be treated for his injuries, which were not life-threatening, Muni spokesman Paul Rose said.