An image forming apparatus, comprising: an image bearing member to bear a toner image on a surface thereof; a transfer device to transfer the toner image onto a recording medium; a sheet separation device to separate the recording medium bearing the toner image on the surface thereof from the image bearing member; a sheet separation bias application device connected to the sheet separation device to apply to the sheet separation device a sheet separation bias in which an alternating current component is superimposed on a direct current component; and a transfer bias application device connected to the transfer device, wherein the transfer bias application device allows to select application of one of a DC transfer bias having a DC component and a superimposed transfer bias in which an AC component is superimposed on a DC component to the transfer device, wherein, upon application of the superimposed transfer bias to the transfer device, the AC component of the sheet separation bias applied to the sheet separation device is changed compared to the AC component of the sheet separation bias applied upon application of the DC transfer bias to the transfer device, wherein in a case in which a normal sheet is fed, the DC transfer bias is applied as the secondary transfer bias and the superimposed bias is applied as the sheet separation bias; and in a case in which a sheet having a coarse surface is fed, the superimposed bias is applied as the secondary transfer bias and the AC voltage of the sheet separation bias is reduced with respect to the AC voltage of the sheet separation bias applied in a case in which a normal sheet is fed. an image bearing member to bear a toner image on a surface thereof; a transfer device to transfer the toner image onto a recording medium; a sheet separation device to separate the recording medium bearing the toner image on the surface thereof from the image bearing member; a sheet separation bias application device connected to the sheet separation device to apply to the sheet separation device a sheet separation bias in which an alternating current component is superimposed on a direct current component; and a transfer bias application device connected to the transfer device, wherein the transfer bias application device allows to select application of one of a DC transfer bias having a DC component and a superimposed transfer bias in which an AC component is superimposed on a DC component to the transfer device, wherein, upon application of the superimposed transfer bias to the transfer device, the AC component of the sheet separation bias applied to the sheet separation device is changed compared to the AC component of the sheet separation bias applied upon application of the DC transfer bias to the transfer device, wherein in a case in which a normal sheet is fed, the DC transfer bias is applied as the secondary transfer bias and the superimposed bias is applied as the sheet separation bias; and in a case in which a sheet having a coarse surface is fed, the superimposed bias is applied as the secondary transfer bias and the AC voltage of the sheet separation bias is reduced with respect to the AC voltage of the sheet separation bias applied in a case in which a normal sheet is fed.