A sheet material conveying device unwinds from a roll body a sheet-shaped member constituting a membrane electrode assembly and conveys the sheet-shaped member. The sheet material conveying device is equipped with a suction member that moves the sheet-shaped member, and a negative pressure supply unit that supplies a negative pressure to the suction member. The suction member is constituted by a porous body capable of sucking under the negative pressure one surface of the sheet material having been unwound from the roll body and is movable in a conveying direction.