Nitriding of 03Kh12N8K5M2TYu maraging steel in a vibrofluidized bed a 480 and 550 °C for 6 h provides the formation on the surface of a diffusion case up to 100-190 μm thick including a nitride area consisting of ε- and γ-phases and a layer of nitrogen martensite hardened by dispersed CrN nitrides. In gas nitriding to obtain this thick a nitrided case a longer hod (up to 30 h) is necessary. Nitriding in a virbofluidized bed for a case of more than 0.2 mm requires a significant increase in process time (up to 20-25 h) and therefore such a treatment is more effective for obtaining a relatively shallow nitrided case.