An image forming apparatus includes a liquid ejection head, a head tank, a liquid storage container, a liquid feed device, a supply valve, an exhaust passage, a float valve, an air release valve, and a suction device. The exhaust passage is disposed in the head tank and communicated with an ambient air. The float valve is disposed in the head tank to close the exhaust passage in response to an amount of liquid in the head tank. The air release valve opens and closes the exhaust passage of the head tank. When the suction device exhausts air from the exhaust passage with the air release valve open, the liquid feed device is driven to pressurize and feed the liquid.