Prosecutors say the bomb, placed by 25-year-old Ramzi Mohammed in July 2005, failed to detonate, and the surveillance tape shows Mohammed running up an escalator entrance once the train arrived at Oval Station in south London.
The tape was played for a London jury last week but was only released publicly late this afternoon.
On the tape, other passengers on board the subway car can be seen trying to get away from Mohammed except for a fireman, Angus Campbell, who bravely stayed to confront Mohammed.
Prosecutor Nigel Sweeney told the jury, "Mohammed said not that it was a bomb but rather, 'What's the matter? It is bread; it isn't me,' pointing at the backpack."
Earlier, the jury was shown surveillance video of Mohammed and others testing the explosive strength of the bombs they planned to plant.
Authorities have yet to fully explain why, if the men were under police surveillance, they were allowed to get on the subway with their bombs, all of which fizzled.
Mohammed and the five others on trial with him have all entered pleas of not guilty.