"Whoever is guilty, even if it is me...we all should abide by the law of the country," he said.
"The country has fully investigated this (case). We salute the law of the land," Bachchan said.
Afzal Guru, who was convicted for his role in the attack on Parliament in 2001, was hanged on Saturday.
Bachchan was talking to reporters on the sidelines of a function in Mumbai.