A method for manufacturing a poppet valve, in which a valve head provided in one end of a valve stem in a longitudinal direction has a seat surface in a direction where an outer diameter is widened toward the one end, by forging an intermediate product of the poppet valve, wherein: the intermediate product of the poppet valve is provided with a large diameter part as the valve head in the one end of the valve stem in the longitudinal direction, wherein the large diameter part is provided with pressing protrusions in a region serving as the seat surface after forging, the pressing protrusions having a peak positioned in a region in a normal direction of the seat surface on a basis of the seat surface of the forged valve head; in a sectional view, the peak of the pressing protrusions is positioned on a normal line passing a reference point set on a virtual line connecting a base point in an inner diameter side and a base point in an outer diameter side of the seat surface; and as viewed in an axial direction of a center line of the valve stem, a position of the reference point is set such that a relation between a length L1 from the base point in the inner diameter side to the reference point and a length L2 from the base point in the outer diameter side to the reference point meets the following formula, L 1 / L 2 ≤ 0.5 the method comprising the steps of: providing a pressing die and a supporting die arranged to face with each other in the center line; supporting the intermediate valve product of the poppet valve by the supporting die in a state of causing the pressing protrusions to abut on a pressing surface of the supporting die between the pressing die and the supporting die, the pressing surface having a shape corresponding to the seat surface; thereafter moving the pressing die in a direction of approaching the supporting die in the center line direction to plastic-deform a region of the pressing protrusions held between the pressing die and the supporting die in the center line direction; and thereby forming the seat surface. the intermediate product of the poppet valve is provided with a large diameter part as the valve head in the one end of the valve stem in the longitudinal direction, wherein the large diameter part is provided with pressing protrusions in a region serving as the seat surface after forging, the pressing protrusions having a peak positioned in a region in a normal direction of the seat surface on a basis of the seat surface of the forged valve head; in a sectional view, the peak of the pressing protrusions is positioned on a normal line passing a reference point set on a virtual line connecting a base point in an inner diameter side and a base point in an outer diameter side of the seat surface; and as viewed in an axial direction of a center line of the valve stem, a position of the reference point is set such that a relation between a length L1 from the base point in the inner diameter side to the reference point and a length L2 from the base point in the outer diameter side to the reference point meets the following formula, L 1 / L 2 ≤ 0.5 the method comprising the steps of: providing a pressing die and a supporting die arranged to face with each other in the center line; supporting the intermediate valve product of the poppet valve by the supporting die in a state of causing the pressing protrusions to abut on a pressing surface of the supporting die between the pressing die and the supporting die, the pressing surface having a shape corresponding to the seat surface; thereafter moving the pressing die in a direction of approaching the supporting die in the center line direction to plastic-deform a region of the pressing protrusions held between the pressing die and the supporting die in the center line direction; and thereby forming the seat surface. providing a pressing die and a supporting die arranged to face with each other in the center line; supporting the intermediate valve product of the poppet valve by the supporting die in a state of causing the pressing protrusions to abut on a pressing surface of the supporting die between the pressing die and the supporting die, the pressing surface having a shape corresponding to the seat surface; thereafter moving the pressing die in a direction of approaching the supporting die in the center line direction to plastic-deform a region of the pressing protrusions held between the pressing die and the supporting die in the center line direction; and thereby forming the seat surface.