The UPSVR said the number of jobless people ready to start work rose by 37,763 on the month to 180,756, while the number of available jobs dropped by 11,072 to 73,602.
Slovakia has had fewer cases of the coronavirus than its neighbours and the more heavily-hit larger European economies, with 1,496 people infected and 28 deaths so far.
But the economy has been hit by disruptions in demand and supply chains that have idled production at some factories, as well as government restrictions on business.
Most of the government restrictions have been lifted in May.