The invention discloses a rock shearing case sealing device. The rock shearing case sealing device comprises a shearing case, a sealing rubber sleeve and a pressure cover, wherein the shearing case is composed of an internal box containing unit for containing a rock sample, both sides of the box containing unit are provided with box connecting units, the size of the inner walls of the box connecting units is larger than that of the inner wall of the box containing unit, and the box containing unit is provided with confining pressure holes for exerting confining pressure; the sealing rubber sleeve comprises a rubber sleeve containing unit for transversely sleeving the outer surface of the rock sample, both sides of the rubber sleeve containing unit are provided with rubber sleeve connecting units, and the peripheral size of the rubber sleeve connecting units is matched with the size of the inner wall of the box connecting units; the pressure cover is fixedly connected with the box connecting units on both sides of the shearing case for pressing the sealing rubber sleeve onto the inner wall of the shearing case and maintaining sealing between the sealing rubber sleeve and the inner wall of the shearing case, and the cover body of the pressure cover is provided with a shearing opening so that a shearing loading pressure head can penetrate through to exert shearing force onto the rock sample.