An image forming apparatus includes: a connector unit to which an external memory device is connected; a detecting unit configured to detect whether the external memory device is connected to the connector unit or not and output a detection result indicating that the connector unit is in a connected state or an unconnected state; a printing unit configured to execute a printing according to data from the external memory device connected to the connector unit; and a suspending unit configured to suspend operation of the printing unit according to a predetermined timing in response to a change in the detection result from the connected state to the unconnected state.