Abstract: A compaction device for a concrete block molding machine, comprising a mold formed with cells opened at the top and at the bottom, and filled with a no-slump concrete mix. The mold freely rests either on a pallet or vibrating table, which acts as bottom wall for the mold. Compaction shoes, equal in number to the number of cells in the mold, are sized, configured and positioned above the mold so that they may snugly fit into the mold cells. The shoes are mounted at the lower ends of power jacks which are connected to a same fluid pressure source or, alternatively, are altogether in fluid communication. The power jacks are operative to move the compaction shoes over the concrete mix in the cells so as to apply to the mix in each cell, preferably, in the final cycle of vibration, an equal compaction pressure suitably selected to produce concrete blocks having a maximum equal density or more uniform desired or selected physical properties.