An image processing apparatus which is capable of realizing security improvements without degrading the usability. A user is authenticated, and an operation screen accepting an operation input from the user is displayed. A job is executed according to an instruction of the user authenticated by the user authenticating unit. It is determined whether or not the job of which execution is instructed by the user, is being executed when the user authenticating unit authenticates the user. A first operation screen through which the user inputs an instruction for the job in execution is displayed when the job executing unit is executing the job, of which execution is instructed by the user, whereas another operation screen through which another user inputs an instruction for another job is displayed when not.