A seat portion (22) includes a first layer (61), a second layer (62), and a third layer (63) that are stacked sequentially from the surface side to the inner side of the seat portion (22). The second layer (62) has a higher stiffness than the third layer (63), and the first layer (61) has a lower stiffness than the third layer (63). A pressure sensitive part (31) has a pressure sensitive-part body (34) arranged between the first layer (61) and the second layer (62).
