David McConaghie was accused of recording a woman in the toilets at MP David Simpson's constituency office.
A court viewed footage showing what appeared to be McConaghie placing the device in a bowl of potpourri.
McConaghie, from Cottage Hill, Dollingstown, denied making recordings for his sexual gratification.
The court heard he had made them over a period of several weeks in August and September 2012.
When the camera was discovered, Mr Simpson immediately reported it to police, and McConaghie resigned his position.
McConaghie will be sentenced in five weeks' time.
In a statement, Mr Simpson said he welcomed the decision by the judge.
"This has been an extremely difficult time for my staff, but particularly for the victims," he added.
Mr Simpson paid tribute to the bravery of his staff in giving evidence and withstanding "a harsh, invasive cross-examination".
A former church minister and DUP adviser accused of secretly filming a colleague for sexual gratification has been found guilty of the offence.