A mobile device with a memo function and a method for controlling the device are provided. The mobile device and method allows a user to input a short note to a privacy memo screen, on which the short note is not displayed during the input process, or to a screen in a locked state. The method includes executing a memo application in the background, and if a user's input for creating a memo is detected through a touch screen, creating a memo in the background through the memo application on the basis of the detected user's input.