Screen display ratio adjusting apparatus and method

A screen display ratio adjusting apparatus includes a handheld device and a display device. The handheld device includes an application module. A display interface of the display device displays a predetermined picture. The predetermined picture includes a first area and a second area extending outward from the first area. The application module is configured to take a current picture. The current picture displays the predetermined picture. The application module is also configured to get a length and a width of the first area from the current picture, and get a length and a width of the second area from the current picture. The application module is further configured to figure out a ratio between the first area and the second area, and configured to adjust a display range of the first area. The display device is configured to display the adjusted display range of the first area. A screen display ratio adjusting method is also provided.