An image forming apparatus includes an image bearing body. A transferring portion transfers an unfixed image in the image bearing body onto a recording material, while conveying the recording material. A fixing portion fixes the unfixed image onto the recording material, while conveying the recording material having the unfixed image is transferred in the transferring portion. A flexure detecting device detects flexure of the recording material between the transferring portion and the fixing portion. A recording material detecting device detects the presence/absence of the recording material at a downstream side of the fixing portion with respect to a conveying direction of the recording material. A control device controls a convey velocity of the recording material in the fixing portion on the basis of a time from the detection of the recording material detected by the recording material detecting device to the detection of the flexure of the recording material detected by the flexure detecting device.