The magnetron reactive ion etching (RIE) characteristics of polycrystalline (poly) 3C-SiC grown on $SiO_{2}$/Si substrate by APCVD were investigated. Poly 3C-SiC was etched by $CHF_{3}$ gas, which can form a polymer as a function of side wall protective layers, with additive $O_{2}$ and Ar gases. Especially, it was performed in magnetron RIE, which can etch SiC at a lower ion energy than a commercial RIE system. Stable etching was achieved at 70 W and the poly 3C-SiC was undamaged. The etch rate could be controlled from $20;{AA}/min$ to $400;{AA}/min$ by the manipulation of gas flow rates, chamber pressure, RF power, and electrode gap. The best vertical structure was improved by the addition of 40 % $O_{2}$ and 16 % Ar with the $CHF_{3}$ reactive gas. Therefore, poly 3C-SiC etched by magnetron RIE can expect to be applied to M/NEMS applications.