A method of making a pleat in a sheet-like material comprising the steps of feeding a flexible and thin sheet-like material having a flat surface in a direction of an extended line of an imaginary straight line which is perpendicular to its one end and along the surface, left and right parts of the sheet-like material being conveyed at a substantially same speed at both sides of the straight line, the one end of the sheet-like material being of a flat form at a start of the feeding, the left and right parts of the sheet-like material being gradually reduced in distance therebetween and drawn near toward the straight line at the middle portion of the extended line so as to face with each other and diagonally cross the surface, and coming in contact with each other perpendicularly to the surface at the forward portion of the extended line, thereby to form the pleat, conveying the sheet-like material through the middle portion to the forward portion with the left and right parts gradually twisted in a direction of the straight line, and fixing both sides of a base portion of the pleat with each other, and an apparatus for carrying out the method are provided. Because the automatic mechanical apparatus is provided to supply the fabric to the sewing device to form the pleat, avoiding unstable manual operations, the fabric can be supplied symmetrically to make the pleat of a desired width, without problems of drops of seams and lateral deflection of the pleat regardless of various conditions of the fabric and size of the intended pleat, keeping a constant tightness of stitches of the seams, whereby complicated manual works for adjusting the feeding conditions can be avoided.