The victims were on a minibus, heading to the wedding in the Dawlatabad district of Balkh province when the blast went off, The News International reported.
At least 18 people were killed and at least 15 others were injured, the BBC said.
Afghan President Hamid Karzai strongly condemned the attack.
"Planting a mine on a road used by civilians and the killing of innocent people represents hostility toward humanity," he said in a statement.
It was not clear who was responsible for the bomb.