There were gasps in the High Court in Aberdeen as the jury convicted Andrew McIntosh, 38, a courier, of 11 charges, including conspiring to force the Government to set up a separate government for Scotland.
The jury of eight men and seven women took two hours and 20 minutes to unanimously find him guilty on 11 charges, including the conspiracy.
The court was told that he had planted eleborate hoax bombs outside four oil industry offices in Aberdeen and letter bombs in postboxes in Glasgow, Edinburgh and Dundee. Explosives experts told the court that the devices were so detailed they thought they were real. One described them as the best hoax bombs seen in Great Britain.
Police raided McIntosh's flat and found a collection of weapons alongside anti-English and 'Free Scotland' posters and literature.
The judge, Lord Morison, said: 'These activities have caused very serious disruption in Scotland and very serious alarm.'
Earlier, the SNLA issued a statement saying that its 'violent struggle' would continue.