A sheet material supplying device includes a tension detection device that detects tensions at both end portions of the unprocessed sheet material in a widthwise direction of the sheet material; an engaging roller that engages the sheet material at a location that is upstream of the processing section in a path of the sheet material that is drawn out; a supporting mechanism that supports both end portions of the engaging roller and that is displaceably supported with respect to the frame such that an axis of the engaging roller is tiltable in a direction that crosses a sheet surface of the sheet material with which the engaging roller engages; an actuator that is connected to the supporting mechanism and that displaces the supporting mechanism; and a drive control device that controls driving of the actuator on the basis of the tensions detected by the tension detection device.