Fire crews were called to the blaze in Port Elphinstone, outside Inverurie, about 1:40pm on Sunday.
The Scottish Fire and Rescue Service said it had nine appliances at the scene on School Road. A height vehicle, command support unit and a water carrier are also in attendance.
A spokeswoman said the “fully developed” fire had taken hold of both floors of the two-storey building.
There are not thought to be any casualties as a result of the blaze.