A man has held a NSW service station up at knifepoint demanding cash, but got away with only a keyboard.

The man robbed the store in Lithgow, in the Central Tablelands, at about 9pm on Wednesday.

After pulling a knife from his sleeve, the man climbed onto the counter and demanded the cash draw from the attendant.

Unsuccessful, he then took the keyboard from the counter before fleeing.

The attendant was unharmed.

Police say the man was wearing a black cap with gold trim, black gloves and a black hooded jumper, and is described as being 180cm tall with a thin build.