Method for manufacturing structure material

A method for manufacturing a structure material product that comprises a thermoplastic resin, reinforced fibers, and voids, the method comprising:

• a first process step of arranging a structure precursor comprising the thermoplastic resin and the reinforced fibers in a mold with a surface temperature of 80° C. or less, the reinforced fibers inside the structure precursor being in a compressed state;
• a second process step of raising the surface temperature of the mold up to a temperature at which a storage elastic modulus (G′) of the structure precursor is less than 1.2×108 Pa so as to raise the reinforced fibers in the compressed state to form the voids;
• a third process step of lowering the surface temperature of the mold down to a temperature at which the storage elastic modulus (G′) of the structure precursor is 1.2×108 Pa or more so as to form the structure material product;
• and
• a fourth process step of removing the structure material product from the mold.