Sudoku is a logic puzzle game that has been encountered since long time ago. Many types of Sudoku have been published, through various electronic media, such as internet and smartphone, and also paper media like newspaper and magazine. However, people may feel uncomfortable if they have to work on the paper. One way to solve this problem is by using an application running on smartphone that is able to capture and digitize the puzzle. This way, people can finish the puzzle with more ease and freedom while they are mobile. To be able to recognize the puzzle grid location, this application makes use of three image processing theories, namely thresholding, region labeling, and perspective transformation. Afterward, Tesseract as an open-source optical character recognition (OCR) library is used in order to recognize each number within the puzzle grid. This Sudoku digitization is designed to run on Android 2.2 smartphone. A number of testing were conducted to examine the application’s functionality. The result shows that from the fifty tests conducted, the application can recognize all of the puzzle positions perfectly. However, from the standpoint of number recognition, the application cannot always recognize each valid number. The best recognition rate of the system is 97.5%, i.e. 78 out of 81 cells are recognized either as numbers or empty cells; while the worst rate is 81.5%, which means only 66 out of 81 cells can be recognized.