His alleged accomplice and association member Ethem Kucuk was acquitted of the same charges.
Both defendants had argued in the case that they displayed their democratic reactions to protest the policies of the government and that this was their constitutional right.
At Thursday's hearing where the verdict was passed, the court decided to postpone Bektasoglu's sentence on grounds that he had no criminal record and displayed good conduct during the trial.
The incident took place on 25 June 2005 in Trabzon during a road opening ceremony where Prime Minister Recep Tayyip Erdogan was making a speech. The defendants threw an egg at the PM while shouting "the henchmen of the Black Sea won't become America's slaves." After a brief detention the two were released to be tried.
PM egg cases continue in Bursa and Mersin
The trial of Selim Kanar also charged with throwing an egg at the Prime Minister in Bursa, the western province of Turkey, started on 11 April. Kanar, a retired worker, faces 2 years imprisonment if found guilty on charges of "insulting the Prime Minister".
In the southern city of Mersin, 9 members of the local Halkevi face up to 13 years 4 months imprisonment each for throwing an egg at Erdogan during an 11 February ceremony held to mark the supply of natural gas to the Organized Industrial areas.
The defendants there are charged both with "insulting senior state officials and public officials" and "violating the law on meetings and public demonstrations". Their hearing has been listed for 24 April. (KO/TK/II/YE)
