Sheet feed device feeding paper and image forming apparatus

A sheet feed device feeding paper including; a loading platen loaded with sheets; a ventilation section providing a first ventilation port for blowing air to float a first side of a sheet of one sheet of the sheets loaded on the loading platen, and a second ventilation port for blowing air to float a second side opposed to the first side; and a control section for controlling the ventilation section; wherein the first side is a side of a topmost of loaded envelopes, the side of which height is lower than other sides, and when envelopes are to be fed, the control section controls the ventilation section to change air volume of the first ventilation port and the second ventilation port so as to float the first side more greatly than in case when sheets other than envelopes are fed.