Transfer device and image forming apparatus including same

A transfer device includes a rotatable image bearing member to bear a toner image on a surface thereof, a nip forming member to contact the surface of the image bearing member, and a bias output device to output a bias current to alternately form a transfer-direction electric field to transfer toner charged with a normal polarity in a toner image formed on the image bearing member to move therefrom to a recording medium and a return-direction electric field to return the toner from the recording medium to the image bearing member. A transition time T1 from a first time at which a current for forming the transfer-direction electric field reaches its maximum (It) to a second time at which a current for forming the return-direction electric field reaches its maximum (Ir) is longer than a transition time T2 from the second time to the first time.