A slicer having two groups of knife blades, each group formed by a plurality of blades, secured side-by-side in two pairs of blade holders. Each pair of blade holders secures one group of knife blades and is provided with a groove between each blade of the supported group through which a blade of the other group of blades passes to define a very narrow opening between adjacent blades. The groups of blades are reciprocated in opposite directions to perform the slicing.