The invention belongs to the technical field of machining, and particularly relates to a mechanical part grinding device which comprises a body component, a driving component and a grinding component,the body component comprises a grinder base, four supporting legs, a grinding wheel fixing table, a workpiece placement plate and a powder collection hopper, the grinder base is a rectangular plate,and the four supporting legs are uniformly distributed at four corners of the bottom of the grinder base. The powder collection hopper is arranged on the lower portion of the grinding wheel, all chippings and spark generated by grinding can enter the powder collection hopper, can be collected and cannot splash throughout to pollute a tabletop, cleaning is omitted after grinding, the mechanical part grinding device is convenient to use, abrasive paper strips are set into a plane strip, a convex surface strip and a concave surface strip, the three abrasive paper strips coaxially rotate, workpieces can be grinded on different abrasive paper strips according to the shapes of the grinded workpieces, the shapes of the grinded workpieces are more, and the mechanical part grinding device is stronger in applicability.