A stereoscopic image printing device includes an actuating unit for moving a grating structure, a print head for transferring a plurality of target image data onto corresponding positions of the grating structure, a first detecting module, a second detecting module, and a controller coupled to the print head, a first photosensitive component of the first detecting module, and a second photosensitive component of the second detecting module for controlling the print head to print some of the plurality of target image data onto the grating structure according to comparison between first optical intensity signal generated by the first detecting module and second optical intensity signal generated by the second detecting module.