The invention provides a sheet feeding device and an image forming apparatus including the sheet feeding device. The sheet feeding device includes a sheet accommodating portion for accommodating a sheet stack, a sheet carrying plate for carrying the sheet stack, a pickup roller that dispatches the sheet of an uppermost layer of the sheet stack, an elevator mechanism that displaces the sheet carrying plate between a sheet feeding position in which the upper face of the sheet stack contacts the pickup roller and a separating position in which the upper face of the sheet stack is separated from the pickup roller, a first warm air mechanism for blowing warm air toward a side face being parallel to the sheet feeding direction, and a controller for controlling the operation of the elevator mechanism and the operation of the first warm air mechanism during a sheet feeding preparation period before starting a sheet feeding operation for feeding a first sheet of the sheet stack. Thereby, miniature can be implemented for the sheet separation mechanism employing warm air assistance.