The utility model provides a belt replacing device for a conveyor. The belt replacing device comprises a power device and an old belt rolling roller driven by the power device, wherein the old belt rolling roller comprises a driving wheel disc assembly, a driven wheel disc assembly and two or more cross beams, wherein the driving wheel disc assembly comprises a driving shaft and a driving wheel disc which is fixedly connected with the driving shaft, the driving shaft is arranged in a supported mode through a bearing I, the driven wheel disc assembly comprises a driven shaft and a driven wheel disc which is fixedly connected with the driven shaft, the driven shaft is arranged in a supported mode through a bearing II, and the driven shaft is in clearance fit with the bearing II. The two ends of each cross beam are fixedly and detachably connected with the driving wheel disc and the driven wheel disc respectively, and each cross beam is at least connected with a traction steel wire rope. According to the belt replacing device, an old belt can be rolled without a special steel wire rope roller, the driven wheel disc can axially move so that the old belt can be taken out conveniently. The belt replacing device is simple in structure and convenient to operate.