The invention relates to the technical field of slitting equipment, and discloses an adhesive tape mother roll slitting device which solves the problem that when a cutter is used for cutting, mucilage glue is prone to adhering to the surface of the cutter, and consequently the cutter becomes blunt. The adhesive tape mother roll slitting device comprises a bottom plate, supporting legs are symmetrically installed on the two sides of the bottom plate, and side plates are symmetrically installed at the top end of the bottom plate; machine body sliding grooves are formed in the sides, close to each other, of the two side plates. A top plate is installed at the top ends of the side plates. In the working process, an output chain wheel of an arranged third motor drives a chain to move, bottom screw rods on the two sides are driven to get close to each other, clamping plates on the two sides clamp an adhesive tape roll, then an output shaft of a second motor rotates reversely, a moving block is driven to move downwards, and then the adhesive tape roll is rolled out; and at the moment, the second motor stops working to adapt to different slitting lengths, and meanwhile, the moving block drives the adhesive tape roll to stretch, so that the pull-down speed is increased, and the slitting efficiency is improved.