PURPOSE: To manufacture of the cushion material even if a core material is above prescribed thickness and it is formed so as to have prescribed hardness by cutting the core material in a desired shape in the transfer direction and forming plural core material pieces, and sewing both skin materials by ultrasonic welding between each core material piece.

CONSTITUTION: A core material 19 passes through between a blade roller 48 and a receiving roller 36, is cut alternately like a corrugated plate and like a straight line by a corrugated plate-like blade 38 and a plate-like blade 39 of the blade roller 48, and plural core material pieces 49 are formed. In each sewn part 31 formed in a gap of each core material 49 by a fact that the upper face side skin material 20 and the lower face side skin material 22 are sewn by press-contacting of a plate-like disk member 23 and an ultrasonic vibrator 11, a liner sewing line 29 is formed. Also, in each sewn part 31 formed in a gap of each core material 49 by a fact that the upper face side skin material 20 and the lower face side skin material 22 by press-contacting of a corrugated plate-like disk member 24 and the ultrasonic vibrator 11, a sewing line 30 consisting of a curve is formed.