A seat pad is made of a flexible polyurethane foam, wherein when the seat pad is divided into five equal parts in a direction of a thickness and the five equal parts are termed from a first layer, to a fifth layer, starting from a front surface side, the equal parts are ranked in the following order of decreasing hardness: the fifth layer, the fourth layer, the third layer, and the second layer. The hardness of the fourth layer is set larger than the hardness of the first layer. A midportion of the seat pad that is a portion other than the front surface and an underside surface is set at a density of 45 to 55 kg/m3.