A female passenger on the bus was taken to Edinburgh Royal Infirmary with serious injuries while two male passengers suffered head and neck injuries.
The driver of the bus, which had 26 people on board, had to be cut free by firefighters following the crash at 10.10pm yesterday.
Three men in the car were taken to hospital, one of them seriously injured.
The crash happened on the B9080 between Kirkliston and Winchburgh.
Another eight people were also taken to hospital.