Provided is a sheet feeding device having a sheet surface detecting mechanism installed to be movable up and down between adjacent adsorption conveyance belts 21, and detects a position of the top surface of the sheet by a sheet surface detecting member 61 that moves upward higher than the adsorbing surface of an adsorption conveyance belt 21. The position of the lower surface of the sheet surface detecting member 61 being pushed up by the blown upward sheet is regulated such that the difference in height between the adsorbing surface of the adsorption conveyance belt 21 and the lower surface of the sheet surface detecting member 61 is smaller than the difference in a height direction between the adsorbing surface of the adsorption conveyance belt 21 and the upper surface of a separation nozzle by a sensor abutting portion 62 that regulates upward movement of the sheet surface detecting member 61.