An image forming apparatus includes an operation unit configured to execute a control method of setting an image forming condition, inputting image data, determining to execute trial image forming, and controlling an image forming device to execute the trial image forming. The control method also includes the steps of accepting a change instruction for changing the set image forming condition, and controlling the image forming device, in a case where the change instruction is accepted, based on inputted image data and the changed image forming condition, and in a case where the change instruction is not accepted, based on inputted image data and the set image forming condition. The method also determines, in the case where the change instruction is accepted, whether or not to again execute the trial image forming.