An image forming apparatus comprising: a photosensitive member to bear an electrostatic latent image on a surface thereof; a charging device to charge the surface of the photosensitive member; a writing device to illuminate a charged surface of the photosensitive member to form an electrostatic latent image on the surface of the photosensitive member; a developing device to develop the electrostatic latent image using toner to form a toner image; a transfer device to transfer the toner image from the photosensitive member to a transfer medium at a transfer position; a charging bias output device to supply a charging bias (Vc) to the charging device; a developing bias output device to supply a developing bias (Vd) to the developing device; a transfer bias output device to supply a transfer bias (Ve) to the transfer device; and a controller operatively connected to the charging bias output device, the developing bias output device, and the transfer bias output device to control the charging bias output device, the developing bias output device, and the transfer bias output device, the controller controlling the transfer bias output device to supply the transfer bias (Ve) from a time at which a first position of the photosensitive member arrives at the transfer position after the charging bias output device starts supplying the charging bias (Vc), wherein the first position of the photosensitive member is a position at which the charging device starts charging the photosensitive member, characterized in that an initial value of the transfer bias (Ve) being controlled to be smaller than a subsequent normal set value for a predetermined time period (Tc) which is a time after the transfer bias (Ve) starts to be supplied and within a time corresponding to a rise time (Ta) during which a surface potential of the photosensitive member reaches a predetermined potential after the charging bias (Vc) starts to be output, wherein the initial value of the transfer bias (Ve) has an effective voltage which is lower than the normal set value which is a value employed upon image formation. a photosensitive member to bear an electrostatic latent image on a surface thereof; a charging device to charge the surface of the photosensitive member; a writing device to illuminate a charged surface of the photosensitive member to form an electrostatic latent image on the surface of the photosensitive member; a developing device to develop the electrostatic latent image using toner to form a toner image; a transfer device to transfer the toner image from the photosensitive member to a transfer medium at a transfer position; a charging bias output device to supply a charging bias (Vc) to the charging device; a developing bias output device to supply a developing bias (Vd) to the developing device; a transfer bias output device to supply a transfer bias (Ve) to the transfer device; and a controller operatively connected to the charging bias output device, the developing bias output device, and the transfer bias output device to control the charging bias output device, the developing bias output device, and the transfer bias output device, the controller controlling the transfer bias output device to supply the transfer bias (Ve) from a time at which a first position of the photosensitive member arrives at the transfer position after the charging bias output device starts supplying the charging bias (Vc), wherein the first position of the photosensitive member is a position at which the charging device starts charging the photosensitive member, characterized in that an initial value of the transfer bias (Ve) being controlled to be smaller than a subsequent normal set value for a predetermined time period (Tc) which is a time after the transfer bias (Ve) starts to be supplied and within a time corresponding to a rise time (Ta) during which a surface potential of the photosensitive member reaches a predetermined potential after the charging bias (Vc) starts to be output, wherein the initial value of the transfer bias (Ve) has an effective voltage which is lower than the normal set value which is a value employed upon image formation.