Manual coffee grinder (10, 10a) for domestic use, of the portable type, which has a vertical development configuration and consists of: - a central body comprising a grinding chamber, a reservoir for whole beans, an inlet opening for said beans which faces upwards; - a closing cover on said inlet opening; - a container for ground powder, which is joined under said central body and can be separated from it; - an external actuating lever, of the crank type, with a lever arm provided with a revolving handle; - a grinding unit joined to said actuating lever, which is integrated into said grinding chamber and comprises two opposite and reciprocally spaced elements, with an interposed hollow space, which crush the beans introduced into said hollow space acting as grinders, where a first grinder is fixed, being integral with said chamber, and a second grinder is rotating, being connected to said actuating lever by means of a rotation shaft, with said shaft, said lever and said grinding unit which rotate coaxially, having the same rotation axis for grinding purposes; - a rotating grain size adjustment ring nut which spaces said grinders from each other, to adjust the grain size of the ground powder; wherein said rotation axis is horizontal and said grinding unit crosses said central body (100, 107) transversely, wherein said actuating lever is located on a side, being connected to one end of said grinding unit, while said grain size adjustment ring nut is located on the opposite side, being connected to the opposite end of the same unit; and wherein said fixed grinder and said rotating grinder are flat and vertical as opposed discs, with said hollow space being vertical; and wherein said fixed grinder is mounted on a flange (128, 128a) fixed to the central body (100, 107) while the rotating grinder is integral with a grinder-holder element which is fixed to the rotation shaft and mounted on ball bearings; and wherein said flange (128, 128a) comprises an inlet conveyor which introduces the beans between the grinders (130a, 130b) by fall from above, directly from said reservoir placed above, with the help of a propeller piece which is connected to said shaft and is integrated into it under said conveyor so that by rotation it removes the beans, pushing them and distributing them in the hollow space between the grinders (130a, 130b); and wherein the powder ground by the grinders (130a, 130b) is introduced by fall into said container placed below, directly from said hollow space, assisted by the rotation of the grinder-holder element (130b, 132) and of the propeller piece. - a central body comprising a grinding chamber, a reservoir for whole beans, an inlet opening for said beans which faces upwards; - a closing cover on said inlet opening; - a container for ground powder, which is joined under said central body and can be separated from it; - an external actuating lever, of the crank type, with a lever arm provided with a revolving handle; - a grinding unit joined to said actuating lever, which is integrated into said grinding chamber and comprises two opposite and reciprocally spaced elements, with an interposed hollow space, which crush the beans introduced into said hollow space acting as grinders, where a first grinder is fixed, being integral with said chamber, and a second grinder is rotating, being connected to said actuating lever by means of a rotation shaft, with said shaft, said lever and said grinding unit which rotate coaxially, having the same rotation axis for grinding purposes; - a rotating grain size adjustment ring nut which spaces said grinders from each other, to adjust the grain size of the ground powder;