Ni nanoparticles were precipitated on Al₂O₃ support powder by rotary chemical vapor deposition (RCVD). The Ni nanoparticle size increased from 8 to 62 nm in diameter and the content of Ni decreased from 6.6 to 2.4 mass % with increasing Al₂O₃ powder diameter (D_Al2O3) from 80 nm to 150 µm. The catalytic activity of Ni precipitated Al₂O₃ (Ni/Al₂O₃) powder was evaluated by the hydrogen production rate (R_H2) in a methanol-steam flow. The R_H2 decreased with increasing D_Al2O3 and increased with increasing specific surface area of Ni/Al₂O₃ powder. The highest R_H2 of Ni/Al₂O₃ powder was 709 × 10⁻³ mol kg⁻¹ s⁻¹ at 633 K, D_Ni = 8 nm and D_Al2O3 = 80 nm.