An image forming apparatus including a print engine, a gloss treatment device, a medium conveying device, and a processor. The print engine is to form an image on a print medium. The gloss treatment device is to perform a gloss treatment on the print medium on which an image is formed. The medium conveying device to provide the print medium to the print engine and selectively provide the print medium on which an image is formed to the gloss treatment device. The processor is to control the print engine to form an image based on print data and control the medium conveying device to selectively provide the print medium to the gloss treatment device depending on whether a gloss treatment option is set in the print data.