An image forming apparatus forms an image on a sheet and conveys the sheet through a conveying path. The image forming apparatus includes a color detection sensor which detects a detection image formed on the sheet for generating an image forming condition and a white reference plate used to calibrate the color detection sensor. The white reference plate is arranged opposite to the color detection sensor with the conveying path interposed therebetween at a position where the white reference plate is not concealed by the sheet when viewed from the color detection sensor when the sheet is conveyed to the conveying path. The detection image is formed on a white reference plate side of the sheet. The color detection sensor reads the white reference plate and is calibrated according to a read result.