Manufacturing method of cushion member

A manufacturing method of a cushion member which has a two-layer structure constituted by an obverse layer portion and a reverse layer portion and has no dispersion of thickness between the obverse layer portion and the reverse layer portion. Side cavities (22), a first cavity (21) and a second cavity (23) are formed in a lower die (2) and side partitions (24) and a front and rear partition (25) are provided therein. A first raw material (41) foams and flows within the first cavity (21), and a second raw material (42) flows within the first cavity while being limited by a front and rear flow port with respect to a flow amount and a flow direction and covers over the first raw material (41) so as to flow forward in such a manner as to follow the flow of a flow front end portion of the first raw material (41). Then, an obverse layer portion and a front edge portion made of the first raw material, and a reverse layer portion made of the second raw material are formed in the first cavity.