A sheet supplying device, including a sheet stacking member which can stack various sized sheets, a side edge alignment member which moves perpendicular to a sheet supplying direction and aligns at least one of side edges of the stacked sheets placed on the sheet stacking member, and an auxiliary side edge alignment member which is provided on the side edge alignment member and ejects in a moving direction of the side edge alignment member and which aligns stacked sheets whose width is narrower than that of the stacked sheets which are to be aligned by the side edge alignment member.