Diamond synthesis on fine metal wire was performed effectively using hot filament chemical vapor deposition (CVD). Diamond deposition is difficult when using wire as a substrate because the substrate overheats easily. Touching the substrate directly with a cooling board is effective in such cases, but that technique is inapplicable in cases having only one wire. Another technique is to keep the substrate away from the heat source filament, thereby maintaining an ideal substrate temperature. However, the greater the distance between the filament and substrate, the lower the deposition rate would be. This study investigated a mode of indirect cooling for diamond deposition that does not lower the deposition rate. Results show that diamond on the wire substrate was deposited at a suitable temperature (900-1000 °C) by indirect cooling without keeping the filament away. The filament was hot enough that atomic hydrogen was generated. A diamond deposition rate of approximately 10 μm/h was attained.