A method for attaching a screen film onto a mobile device, comprising: a preparing step implemented by providing a screen film applicator and a screen film structure, wherein the screen film structure includes: a transparent screen film having a first surface and a second surface opposite to the first surface; a first release film including: a first main portion detachably adhered to the first surface of the screen film, wherein a peripheral edge of the first main portion is substantially aligned with a peripheral edge of the screen film; and a first aligning portion connected to the first main portion and protruding out of the screen film, wherein the first aligning portion has a plurality of first positioning holes; and a second release film detachably adhered to the second surface of the screen film, wherein the screen film is a glass screen film, the peripheral edge of the screen film includes two long lateral edges parallel to each other and two short lateral edges parallel to each other, and the first aligning portion protrudes out of one of the two long lateral edges, and wherein the screen film applicator includes: a seat including an accommodating trough recessed in a top surface thereof, the accommodating trough having a long inner wall and a short inner wall; a plurality of positioning pillars extending from the top surface of the seat and arranged adjacent to the long inner wall of the seat; and a clamping mechanism movably arranged in the accommodating trough; a clamping step implemented by placing a mobile device in the accommodating trough and using the clamping mechanism to press the mobile device to abut against the long inner wall and the short inner wall, wherein a screen of the mobile device faces toward a direction away from the seat; a film aligning step implemented by taking the second release film to face the screen (Cl) of the mobile device and taking the first release film to dispose the positioning pillars in the first positioning holes; and an attaching step implemented by tearing the second release film away from the second surface of the screen film and then adhering the second surface of the screen film onto the screen of the mobile device. a preparing step implemented by providing a screen film applicator and a screen film structure, wherein the screen film structure includes: a transparent screen film having a first surface and a second surface opposite to the first surface; a first release film including: a first main portion detachably adhered to the first surface of the screen film, wherein a peripheral edge of the first main portion is substantially aligned with a peripheral edge of the screen film; and a first aligning portion connected to the first main portion and protruding out of the screen film, wherein the first aligning portion has a plurality of first positioning holes; and a first main portion detachably adhered to the first surface of the screen film, wherein a peripheral edge of the first main portion is substantially aligned with a peripheral edge of the screen film; and a first aligning portion connected to the first main portion and protruding out of the screen film, wherein the first aligning portion has a plurality of first positioning holes; and a second release film detachably adhered to the second surface of the screen film, wherein the screen film is a glass screen film, the peripheral edge of the screen film includes two long lateral edges parallel to each other and two short lateral edges parallel to each other, and the first aligning portion protrudes out of one of the two long lateral edges, and wherein the screen film applicator includes: a seat including an accommodating trough recessed in a top surface thereof, the accommodating trough having a long inner wall and a short inner wall; a plurality of positioning pillars extending from the top surface of the seat and arranged adjacent to the long inner wall of the seat; and a clamping mechanism movably arranged in the accommodating trough; a seat including an accommodating trough recessed in a top surface thereof, the accommodating trough having a long inner wall and a short inner wall; a plurality of positioning pillars extending from the top surface of the seat and arranged adjacent to the long inner wall of the seat; and a clamping mechanism movably arranged in the accommodating trough; a clamping step implemented by placing a mobile device in the accommodating trough and using the clamping mechanism to press the mobile device to abut against the long inner wall and the short inner wall, wherein a screen of the mobile device faces toward a direction away from the seat; a film aligning step implemented by taking the second release film to face the screen (Cl) of the mobile device and taking the first release film to dispose the positioning pillars in the first positioning holes; and an attaching step implemented by tearing the second release film away from the second surface of the screen film and then adhering the second surface of the screen film onto the screen of the mobile device.