An image forming apparatus includes a treatment-liquid application unit applying a treatment liquid from a chamber to a recording medium; a treatment-liquid storage unit to store the liquid; a supply channel member forming a supply channel to supply the liquid from the treatment-liquid storage unit to the chamber; a collection channel member forming a collection channel to collect the liquid from the chamber; and a temporary storage portion disposed in the collection channel to temporarily store the liquid. The temporary storage portion has an internal horizontal cross-sectional area greater than a channel cross-sectional area of the collection channel. The collection channel member has a first channel portion of a channel cross-sectional area smaller than the internal horizontal cross-sectional area of the temporary storage portion. A liquid level of the liquid in the collection channel is maintained in the first channel portion after termination of collecting operation.