An image forming apparatus includes an image bearing drum; a drum charging member, disposed at a charging position opposed to the drum, for applying the drum with a charging bias; a developing member for developing an electrostatic image formed on the drum with toner, with a developing bias; a transfer member for transferring a toner image from the drum onto a sheet, with a transfer bias; a transfer bias source for outputting the transfer bias; and a controller for effecting control to start raising of the transfer bias so as to correspond to a timing at which an area of the drum passing at a timing of starting of raising of the charging bias passes the transfer position and to complete the raising of the transfer bias so as to correspond to a timing at which an area of the drum passing at a timing of completion of raising of the charging bias passes the transfer position.