The purpose of the present invention is to eliminate the need for manual sewing of a three-fold seam and for the sheet-by-sheet supply of material. This sewing device comprises: a needle gripper (64) capable of gripping a material (110) stored in a magazine (52) one sheet at a time; a moving stage (15) which receives the material (110) gripped by the needle gripper (64); a fixed stage (17); a first feed section (18) which turns one edge (111) of the material (110) placed in a second placement position (17b) on the fixed stage (17) into a three-fold; a first pressing plate (21) which feeds the material (110) placed in a first placement position (17a) on the fixed stage (17) to the second placement position (17b); a second pressing plate (22) which feeds the material placed on the moving stage (15) to the first placement position (17a) on the fixed stage (17); and a sewing machine (13) which sews the one edge (111) of the material (110) that has been turned into a three-fold by the first feed section (18).