1. An image forming apparatus for executing a processing flow including a plurality of steps, comprising: a determination unit adapted to determine whether or not a processing flow to be executed includes an instruction required step that requires an instruction of a user; a selection unit adapted to select, when the processing flow to be executed includes the instruction required step, a notification destination of information required to display an operation window for accepting the instruction of the user; a notification control unit adapted to notify the notification destination selected by said selection unit of the operation window; and an execution unit adapted to execute processing of the instruction required step according to instruction contents input via the operation window.