A lens blocker comprising: a drive cam of a cylindrical shape; a blocker arm coupled to the drive cam to be movable up and down along the drive cam or to be rotatable about the drive cam; a leap block mount, to which a leap block to be attached to a blank lens is mounted and which is coupled to the other end of the blocker arm; a blocker arm base configured to move the blocker arm up and down along the drive cam; and a lens mount onto which the blank lens, to which the leap block is to be attached, is mounted; characterized in that the drive cam has a blocker arm guide groove formed therein; the blocker arm has a blocker arm guide formed at one end thereof, wherein the blocker arm guide is inserted into the blocker arm guide groove of the drive cam 30 and moves along the blocker arm guide groove, so as to cause the blocker arm to move up and down along the drive cam or to rotate about the drive cam; the drive cam further comprises a leap block mount guide groove formed therein; wherein the leap block mount comprises: a block rotation portion on which the leap block to be attached to the blank lens is mounted and which is coupled to the other end of the blocker arm so as to be rotatable up and down; a block rotation shaft, one end of which is fixedly coupled to the block rotation portion and which extends through the blocker arm; and a leap block mount guide coupled to and spaced by a predetermined distance from the center of the other end of the block rotation shaft, and configured to be inserted into the leap block mount guide groove of the drive cam so as to move along the leap block mount guide groove; and wherein at an initial position (a) where the leap block is mounted to the leap block mount, the leap block mount is positioned toward an upward direction, and at an attachment position (b) where the leap block is attached to the blank lens, the leap block mount is positioned toward a downward direction. a drive cam of a cylindrical shape; a blocker arm coupled to the drive cam to be movable up and down along the drive cam or to be rotatable about the drive cam; a leap block mount, to which a leap block to be attached to a blank lens is mounted and which is coupled to the other end of the blocker arm; a blocker arm base configured to move the blocker arm up and down along the drive cam; and a lens mount onto which the blank lens, to which the leap block is to be attached, is mounted; characterized in that the drive cam has a blocker arm guide groove formed therein; the blocker arm has a blocker arm guide formed at one end thereof, wherein the blocker arm guide is inserted into the blocker arm guide groove of the drive cam 30 and moves along the blocker arm guide groove, so as to cause the blocker arm to move up and down along the drive cam or to rotate about the drive cam; the drive cam further comprises a leap block mount guide groove formed therein; wherein the leap block mount comprises: a block rotation portion on which the leap block to be attached to the blank lens is mounted and which is coupled to the other end of the blocker arm so as to be rotatable up and down; a block rotation shaft, one end of which is fixedly coupled to the block rotation portion and which extends through the blocker arm; and a leap block mount guide coupled to and spaced by a predetermined distance from the center of the other end of the block rotation shaft, and configured to be inserted into the leap block mount guide groove of the drive cam so as to move along the leap block mount guide groove; and wherein at an initial position (a) where the leap block is mounted to the leap block mount, the leap block mount is positioned toward an upward direction, and at an attachment position (b) where the leap block is attached to the blank lens, the leap block mount is positioned toward a downward direction.