Recycling of persistent materials is one of most important subjects to be addressed towards the sustainable society. Amyloid fibril is such a tough biomaterial that can be designed for various industrial applications, and it is usually difficult to dissociate the once made fibrous conformation due to the cross β-sheet stacks. We propose here a unique but versatile approach to handle the fibril formation by using two-kinds of high-power terahertz waves. Lysozyme and β2-microglobulin peptide fragment were employed as model samples, and those fibrils were clearly disaggregated accompanied by decrease of β-sheets and increase of α-helices by the irradiation of 5.3 THz free electron laser tuned to 56 μm, as shown by infrared (IR) microscopy and scanning-electron microscopy (SEM). In contrast, those fibrous conformations were reversely self-associated by the irradiation of 0.42 THz wave tuned to 720 μm from gyrotron, as shown by optical and IR microscopies, SEM, and small-angle X-ray scattering. The overall reaction is performed at room temperature within 30 min without external heating and high-pressures. Therefore, amyloid fibrils can be dissociated and associated under the proper far-infrared radiation conditions, which inspires a sustainable recycling system of fibrous biomaterials.