An image forming apparatus in accordance with the present invention includes a vibration sensor that transmits a detection signal in response to a vibration pattern and a sheet feeder cassette unit that stores recording papers, is opened/closed by extraction/insertion, and generates a specific vibration pattern while being opened or closed. The image forming apparatus includes an open/close detector unit that detects an opened/closed state of the sheet feeder cassette unit when detecting a predetermined vibration pattern based on the detection signal of the vibration sensor.