A glass substrate laser cutting device according to the invention includes: a working table that has a plurality of vacuum absorbing grooves; a laser cutter; a pressure sensor that measures a pressure sensor when suctioning the glass substrate in a vacuum state; a calculation processing unit that compares the vacuum pressure measured by the pressure sensor with a predetermined threshold pressure and determines whether the glass substrate is broken; a laser cutter that includes a leaser head moving along the cutting direction of the glass substrate and emitting a laser beam; and an optical sensor that is attached to the laser head so as to move together and is disposed at a point in front of the laser beam emitted to the outside so as to detect the breakage of the glass substrate.