In an image forming apparatus, a pre-transfer guide (50) is provided immediately before a transfer nip portion formed by an intermediate transferring belt (12) and a transferring roller (18b). The pre-transfer guide (50) extends in a width direction of a sheet conveying path, and projections (50b) are formed on opposite end portions of the pre-transfer guide (50) on sides outer than an area on which a sheet is conveyed. The intermediate transferring belt (12) is driven in a state where a tension is applied to some extent, so that it may bow in a thickness direction on a running path. However, in an area immediately before the transfer nip portion, the projections (50b) retains a distance between the sheet and the intermediate transferring belt (12) to be greater than a predetermined distance.