The blaze was discovered at Greenside, Speddoch last Friday night at about 9.45 pm and the emergency services were called.
Police Scotland are now investigating and Constable Danielle Moore said: “A joint examination of the barn has revealed that this fire has been a deliberate act.
The value of the bales destroyed and damage to property could be in the region of £2000.
We are asking anyone who may have any information which might help us catch those involved to call us on the 101 number. The barn in question is only a matter of some 30 metres from the farm house, and had the fire spread then the consequences could have been catastrophic.”
Anyone with any information should call 101 and quote the reference number 4467 of 31/8.