The invention relates to a medicine grinding device. The medicine grinding device comprises a drive component area, a breaking device, a grinding chamber, a water circulation system and a finished product conveying chamber. No temperature rise of a breaking shaft and a grinder during working is ensured through reasonable arrangement for the water circulation system, so that the occurrence of a caking case of a medicine powder is greatly avoided. A grinding period is prolonged through reasonable configuration for a shape of the grinder and reasonable arrangement for a matched grinding groove, so that a grinding effect is enhanced. A sheet caking case existing in the powder before conveying is greatly improved through improvement for a conveying chamber.