The present invention discloses a laser dicing apparatus for a gallium arsenide wafer and a method thereof, wherein firstly, a gallium arsenide wafer is stuck onto a holding film; next, the gallium arsenide wafer together with the holding film is disposed on a working table; the gallium arsenide wafer has multiple chips or dice with a scribed line drawn between every two chips; a control device and an object lens are used to position the working table and a laser, and two video devices are used to observe whether the laser has been precisely aimed at one of the scribed lines; after parameters have been input into the control device, the laser is used to cut the gallium arsenide wafer, and the gallium arsenide wafer is then separated into multiple discrete chips or dice. The present invention can precisely cut gallium arsenide wafers, reduce the cost and accelerate the fabrication process.